Prominent differences between dialects of Spanish include the distinction or lack thereof between /θ/ or /s/. The maintenance of the distinction, known in Spanish as distinción or by the neologism ceseo, is characteristic of the Spanish spoken in northern and central Spain. Most dialects of Latin America and Southern Spain lack this distinction, and have merged the two sounds into /s/, a feature called seseo in Spanish dialectology. Dialects with seseo will pronounce the words casa ("house") and caza ("hunt") as homophones, whereas dialects with distinción will pronounce them differently (as [kasa] and [kaθa], respectively). In some parts of Andalusia, the two sounds have merged, but into sounds [θ]; these dialects are said to have ceceo.
Another widespread dialectal difference concerns the existence, or lack thereof, of a distinction between the palatal lateral (spelled ll) and the palatal approximant (spelled y). In most dialects, the two sounds have merged together (a process known as yeísmo), though the realization of the resulting merged sound varies from dialect to dialect. This merger results in the words calló ("silenced") and cayó ("fell") being pronounced the same, whereas they remain distinct in dialects that have not undergone this merger.
Another feature associated with many varieties, like those in the southern half of Spain, the Caribbean and most of South America, is the weakening (to [h]) or loss of the consonant /s/ when syllable-final (/s/ debuccalization). This feature, called aspiración de las eses in Spanish, is associated in certain regions with other phonetic changes, like the opening of the previous vowel or the modification of the following consonant.
A prominent grammatical feature that varies between dialects is the use of the 2nd person forms. In most of Spain, the informal second person plural pronoun is vosotros, which is not used in Latin America, where the only second person plural pronoun is ustedes, which takes third person plural verb agreement. For the second person singular familiar pronoun, some dialects use tú, while others use vos (a phenomenon known as voseo), or use both tú and vos.
There are significant differences in vocabulary between regional varieties of Spanish, particularly within the domains food products, everyday objects, and clothes, and many Latin American varieties show considerable influence from Native American languages.
Since some words would become homophones in Latin America with the confusion of the pronunciation of z or c before e or i and that of s, it is preferred to use instead synonyms or slightly different words. E.g., caza ("hunting") and casa ("house") become homophones, as do cocer ("to boil") and coser ("to sew"). So, in Latin America they use instead mostly cacería ("hunting expedition") and cocinar (which means "to cook" in other dialects).
In most of Latin America (except for Mexico, highland Guatemala, Costa Rica, Andean Venezuela, Quito and most of highland Ecuador, highland Bolivia, and Bogotá) and in the southern half of Spain, syllable-final s is pronounced as an aspiration (a voiceless glottal fricative, /h/), or even not pronounced at all in some variants in rapid speech. For instance, Todos los cisnes son blancos ("All the swans are white"), can be pronounced as , or even . In eastern Andalusia and part of the Region of Murcia, the distinction between syllables with a now-silent s and those originally without s is preserved by pronouncing the syllables ending in s with open vowels (that is, the open/closed syllable contrast has been turned into a lax/tense vowel contrast); this typically affects the vowels 'a', 'e' and 'o', but in some areas even 'i' and 'u' have a double set of phonemes.
Several variants of Spanish are also characterized by a highly relaxed pronunciation, which tends to aspiration or elision of many implosive consonants, not just final s. This is not related to the elision of k in the pronunciation of x, which is general in most dialects of Spanish, except in formal speech. However, s is reinforced because of its dental, stressed realization, in some kind of assimilating phenomenon. Something similar occurs with other sibilant groups, like -sc-, -sz- or -xc- in seseo areas. Thus words like examen ("exam") or próximo ("nearby", "next") are pronounced as [esˈsamen] and [ˈprossimo], respectively, and words like descenso or excelencia in seseo areas become [desˈsenso] or [ɛsseˈlɛnsja]. Due to this tendency, it is not unusual to find similar cases of s assimilation and reinforcement even in cases where two s letters are added through prefixation into a single word, producing only a single s in Standard Spanish, and Northern or Latin American Speech: for example in digámoselo ("let's tell it to them"), formed from the verbal form digamos and clitic pronouns se and lo, a typically Andalusian pronunciation would be [diˈɡamosselo], or in desaborido ("untasteful" or "boring", "pessimistic"), from the prefix des ("un-") plus adjective saborido ("tasteful"), an Andalusian pronunciation would be [(d)essaboˈrido].
An exception is the pronunciation of the x in words like México, which originally used the phonetic value of the x in Medieval Spanish, represented by the voiceless postalveolar fricative /ʃ/. This evolved into a voiceless velar fricative /x/ during the sixteenth century. Although the name is still spelled México, the x sounds like /x/. This is also true for other toponyms, like Texas and Oaxaca and proper and last names like Xavier and Ximénez.
The phoneme /ʝ/ can also be pronounced in a variety of ways. In most of the area where yeísmo is present, the merged phoneme is pronounced just as /ʝ/, or even /j/. In the area around the Río de la Plata (Argentina, Uruguay) this phoneme is pronounced as a postalveolar fricative, voiceless or weakly voiced (similar to /ʃ/ or /ʒ/).
In any case, there is wide variation as to when each pronoun (formal or informal) is to be used. In Spain, tú is informal (for example, used with friends), and usted is formal (for example, used with older people). There has been a noticeable tendence to extend the use of tú even in situations previously reserved for usted. In several countries, however, the formal usted is also used to denote a closer personal relationship (parts of Central America and, especially, in Colombia). Many Colombians and some Chileans, for instance, employ usted not only for a child to address a parent, but also for a parent to address a child. Some countries, like Cuba and the Dominican Republic, prefer the use of tú even in very formal circumstances, and usted thus is seldom used. Meanwhile, in other countries, the use of formal rather than informal second-person pronouns denotes authority. In Peru, for example, senior military officers will use tú to speak to their subordinates, while junior officers will use only usted to address their superior officers.
Using tú informally, especially in contexts where usted was to be expected, is called tuteo. The corresponding verb is tutear (a transitive verb, the direct object being the person addressed with the pronoun). Tutear is used even in those dialects where the informal pronoun is vos.
The use of vos instead of tú is called voseo. Voseo is informal in most countries. In Nicaragua, Honduras, Paraguay, Argentina and Uruguay it is the standard form of the informal second person singular, and is used by all to address others in all kinds of contexts, often regardless of social status or age, including by cultured/educated speakers and writers, in television, advertisements, and even in translations from other languages. In Uruguay vos and tú are used concurrently, though vos is much more commonplace. In both cases the verb is conjugated as vos ("Vos querés / Tú querés", rather than "Vos querés / Tú quieres").
The name Rioplatense is applied to the particular dialect, spoken around the mouth of the Río de la Plata and the lower course of the Paraná River, where vos is always used, with verb conjugations that resemble those of the Castilian second person plural. This area comprises the most populated part of Argentina (the provinces of Buenos Aires and Santa Fe) as well as an important part of Uruguay including Montevideo, the capital.
In Ecuador, vos is also the most prominent form throughout the country, though it does coexist with usted and the lesser used tú. Vos is regarded as the unofficial standard, but it is not used in public discourse, the media or television. To complicate things more, in Ecuador the choice of pronoun to be used depends on the participants' likeness in age and/or social status. Based on these factors, the addresser can assess himself as being an equal, superior or inferior to the addressee, and the appropriate choice of pronoun to be employed can then be made. Ecuadorians generally use vos among familiarized equals, or by superiors [in both social status and age] to inferiors; tú among unfamiliarized equals, or by a superior in age but inferior in social status; and usted by both familiarized and unfamiliarized inferiors, or by a superior in social status but inferior in age.
Vos can be heard throughout most of Chile, Bolivia, and a small part of Peru as well, but in these places it is reproached as substandard and the speech of the uneducated and ignorant. It is also used as the unofficial standard in the Paisa Region (Colombia), in Zulia (Venezuela), in Honduras, El Salvador, Costa Rica, Guatemala, and the State of Chiapas in Mexico.
In Chile, tú is the preferred pronoun in all normal and educated speech. Vos is used, pronounced with an aspiration at the end instead of s. When so pronounced, it is always derisive to some extent, with the magnitude of this disdain depending on the inflection of speech. In this form, it is used in informal speech between very close friends as playful banter (usually among men), but even then a change in inflection can change the meaning of a statement, which can result in an offensive comment. The use of verbal voseo (tú + vos conjugation of the verb, e.g. "tú podís") is quite widespread, though. This has been something that typically distinguishes Chileans.
A usage similar to voseo is vos with the verb in the grammatically plural form (as if it were vosotros). It appears as a formal or disrespectfully familiar use in the works of the Spanish Golden Century/Golden Age and period works placed in that era. In Colombia, the choice of second person singular varies with location. In most of inland Colombia (chiefly the Andean region), usted is the pronoun of choice for all situations, even in speaking between friends or family, but in large cities (Bogotá mainly), the use of tú is becoming more accepted in informal situations, especially between young interlocutors of the opposite sex and among young women. In Valle del Cauca (Cali), Antioquia (Medellín) and the Pacific coast, the pronouns used are vos/usted. On the Caribbean coast (mainly Barranquilla and Cartagena), tú is used for practically all informal situations and many formal situations, usted being reserved for the most formal environments. A peculiarity occurs in Boyacá and among older speakers in Bogotá: usted is replaced by sumercé for formal situations (it is relatively easy to spot a Boyacense by his/her use of this pronoun). Sumercé comes from su merced ("your mercy").
In parts of Spain, fifty years ago a child would not use tú but usted to address a parent. This would be very unusual today. Among the factors for the ongoing substitution are the new social relevance of youth and the reduction of social differences. Being addressed as usted makes one feel older. It has also been attributed to the egalitarianism of the right-wing party Falange. By contrast, Spanish leftists of the early 20th century would address their comrades as usted as a show of respect and worker's dignity.
Joan Corominas explains that vos was a peasant form in classical Castilian, and since most Spanish immigrants to the New World belonged to this class, vos became the unmarked form.
Another explanation is that in Spain, although vos denoted high social status by those who were addressed as such (monarchs, nobility, etc.), these people never actually used the pronoun themselves since there were not any people above them in society. Those who used vos were the inferiors (lower classes and peasants). When the waves of Spanish immigrants arrived to populate the New World, they were primarily comprised of these lower classes and peasants. They would then want to raise their social status from what it was in Spain and would demand to be addressed as vos. Everyone thus became vos in the Americas, and the pronoun was transformed into an indicator of low status not only for the addresser, but also for the addressee. Conversely, in Spain today "vos" is still considered a highly exalted archaism that is confined to liturgy, and its use by native Spaniards is seen as deliberate archaism.
Speakers of Ladino still use vos as it was originally used, to address people higher on the social ladder. The pronoun usted had not been introduced to this dialect of Spanish when the Jews were expelled from Spain in 1492, hence vos is still used in Ladino much as usted is used in modern Spanish.
Other less frequent forms analogous to usted are voacé, bosanzé and boxanxé (by Moriscos), vuecencia, v/usía. The latter are short for vuestra excelencia and vuestra señoría. The most common analogous form of usted still used today is vusted, which can be heard in Andean regions of South America.
In Argentina, Colombia, Peru, and Chile, school children are taught the conjugation of vosotros and are not taught to use ustedes at all. However, it is only a formality, as they rarely if ever use vosotros in real-life situations.
The only vestiges of vosotros in America are boso/bosonan in Papiamento and the use of vuestro/a in place of sus (de ustedes) as second person plural possessive in the Cusco region of Peru.
Joan Coromines supposes that the vos forms in the Caribbean were perceived as slave-talk, and disrespectful for whites initially, and later for everybody.
The plural of the Colombian sumercé is sumercés/susmercedes, from Sus Mercedes ("Your Mercies").
In Ladino vosotros is still the only second person plural pronoun, since usted does not exist.
The term voseo also applies when a pronoun other than vos is used but the verb immediately following is nonetheless conjugated according to the norms of vos: hence "tú subís, tú decís, tú querés" is still considered voseo.
In standard Castilian Spanish, the compound tense is preferred in most cases when the action described is close to the present moment:
However, in parts of Spain (Galicia, León, Asturias) and Latin America speakers follow the opposite tendency to use the simple past tense in most cases, even if the action takes place at some time close to the present:
Indeed, in Latin America, the compound past tense is used rarely, most notably when the action has been finished recently, to stress its immediacy, much like the present perfect in English, but even in those cases the simple past tense is prevalent:
In this dialect, the first example of the compound past given above (Yo he viajado...) is grammatical, though it sounds affected or foreign. In fact, most Latin Americans would perceive Spaniards as uneducated due to their excessive use of the compound tense. However, this tendency in Spain is regional (mostly in the Castilian dialect, although it is used in standard Spanish in Spain, and thus frequently heard in the media), and is not prevalent in the rest of Spain. Both French and Italian tend to use the compound tense when the simple past would be more suitable in Spanish. The second example (Cuando he llegado), however, would be considered grammatically incorrect due to the presence of the compound tense in the clause started by cuando ("when").
In Latin America one could say "He viajado a España varias veces", "I have travelled to Spain several times", to express frequency or tendency like in English. It would be utterly incorrect to say "Ayer, he viajado a España" or "Yesterday, I have travelled to Spain", since it was a definite past stressed by the word yesterday. In Spain, people use the "haber + verb" to express things done in the past when the period of time considered hasn't ended, like "he comprado un coche este año" "I have bought a car this year". A Latin American would correct the individual by saying "Compré un coche este año" meaning "I bought a car this year".
More examples of the way in which the 2 tenses are used in most of Spain :
However, Malmberg and others have pointed out that in Mexican Spanish, it is vowels that lose strength, while consonants are fully pronounced. It has been pointed out that Mexican Spanish is tending towards stress timing and concomitant vowel reduction, and that this is likely to be caused by the influence of geographically close English of the United States and strong economic and social-cultural ties between the two countries. Other theories associate vowel reduction in Mexico with a native American substratum, in fact vowel reduction is not unknown along the Andean area (higland Colombia, Bolivia, Peru) where the influence of native American languages was strong on Spanish.
Prescription and a common cultural and literary tradition, among other factors, have contributed to the formation of a loosely-defined register which can be termed Standard Spanish (or "Neutral Spanish"), which is the preferred form in formal settings, and is considered indispensable in academic and literary writing, the media, etc. This standard tends to disregard local grammatical, phonetic and lexical peculiarities, and draws certain extra features from the commonly acknowledged canon, preserving (for example) certain verb tenses considered "bookish" or archaic in most other dialects.