Deva (देव in Devanagari script, pronounced as /'d̪ev.ə/) is the Sanskrit word for "god, deity". It can be variously interpreted as a god, spirit, demi-god, celestial being, deity or any supernatural being of high excellence. They are opposed to the usually demonic Asuras.
The cognate word in Avestan is daeva, which has a pejorative connotation. In later Zoroastrianism, daevas are noxious creatures, but this meaning is not evident in the oldest texts. The Mitra-Varuna pair in the Rig Veda is strikingly similar to the Mithra-Ahura pair in the Yasna. In the Zend Avesta, however, Daevas are portrayed with warlike qualities as opposing forces of the Ahuras (cognate with Asuras). The origin of the word devil can be traced back to Mithraism.
Also cognate to deva are the Lithuanian Dievas (Latvian Dievs, Prussian Deiwas), Germanic Tiwaz (seen in English "Tuesday") and Latin deus "god" and divus "divine", from which the English words "divine", "deity", French "dieu", Spanish "dios" and Italian "dio" are derived.
Related but distinct is the PIE proper name *Dyeus which while from the same root, may originally have referred to the sky, and hence to "Father Sky", the chief god of the Indo-European pantheon, continued in Sanskrit Dyaus. The Romani word for God, del or devel, is directly descended from devat?.
The Upanishads distinguish between the celestials gods from the Divine forms of God. The Brihadaranyaka Upanishad says there are 33 gods in the celestial world, in terms of performance of Vedic rituals and yajnas. They are eight Vasus, eleven Rudras, twelve Adityas, Indra, and Prajapati. The pantheon in the Śrauta tradition consists of various gods and goddesses. The main celestial gods or devas are (vide 6th anuvaka of Chamakam):
The main Devis (goddesses) are:
Some devas represent the forces of nature and some represent moral values. The main deva addressed in the Rig Veda is Indra. Agni (fire) and Soma represent modes of fire-sacrifice, called yagna, but personified are also seen as devas. Aitareya Brahmana in its opening stanza suggests a hierarchy among devas. All gods taken together are worshipped as the Vishvedevas. Varuna, has the dual title of deva and asura. There are also other devas like Savitŗ, Vishnu, Rudra (later given the exclusive epithet of Shiva, "auspicious one"), Prajapati (later identified with Brahmā), and devis (goddesses) like Ushas, Prithvi and Sarasvati (sky, earth, and water respectively).
There are also many other lesser celestial beings in Hinduism such as Gandharvas or celestial musicians.
Devas, in Hinduism, are celestial beings that control forces of nature such as fire, air, wind, etc. They are not to be confused with the One and the Supreme God or His personal form, Saguna Brahman which can be visualized as Vishnu or Shiva. God (see Ishvara) or Brahman (the Supreme Spirit) is the ultimate controller. A famous verse from the Katha Upanishad states: “From fear (here, power) of Him the wind blows; from fear of Him the sun rises; from fear of Him Agni and Indra and Death, the fifth, run." In actuality, Brahman is the only Ultimate Reality, and all devas are simply mundane manifestations of Him.
The Vaishnavites (who often translate deva as "demigod") cite various verses that speak of the devas' subordinate status. For example, the Rig Veda (1.22.20) states, : "All the suras (i.e., the devas) look always toward the feet of Lord Vishnu." Similarly, in the Vishnu sahasranama the concluding verses state: "The Rishis (great sages), the ancestors, the devas, the great elements, in fact all things moving and unmoving constituting this universe, have originated from Narayana," (i.e., Vishnu). Thus the devas are stated to be subordinate to Vishnu, or God.
In the Bhagavad Gita Krishna himself states that worshipers of deities other than the Supreme Lord, Vishnu, are incorrect (Gita 9.23) as such worship leads only to temporal benefits, rather than to the Lord Himself (Gita 7.23). Krishna also says: "Whatever deity or form a devotee worships, I make his faith steady. However, their wishes are granted only by Me." (Gita: 7:21-22) Elsewhere in the Gita Lord Krishna states: "O Arjuna, even those devotees who worship other lesser deities (e.g., devas, for example) with faith, they also worship Me, but in an improper way because I am the Supreme Being. I alone am the enjoyer of all sacrificial services (Seva, Yajna) and Lord of the universe." (Gita: 9:23)
Swaminarayan, the founder of the Hindu Swaminarayan sect, a Vaishnavite sect, according to this site, , said in verse 115 of their scripture, Shikshapatri, "Shree Krishna Bhagwan and Shree Krishna Bhagwan's incarnations alone are worthy of meditation. Similarly, Shree Krishna Bhagwan's images are worthy. And men or devas, even if they are devotees of Shree Krishna Bhagwan or brahmavettaa (knowers of divinity), are still not worthy of meditation - and thus one should not meditate upon them."