As of 2015, the tongue twister that the Guinness Book of World Records noted as the most difficult in the English language is, "The sixth sick sheik's sixth sheep's sick." Tongue twisters are difficult to articulate properly and are often used with the intent to provide amusement.
Some tongue twisters are used in games or are sung as songs. "She sells sea-shells on the sea-shore," is a popular, yet difficult, tongue twister that was included in a song written by Terry Sullivan.
Other tongue twisters utilize a rhyme and rhythm combination that requires repositioning of the tongue between syllables to increase the level of difficulty of speaking the phrase. One example of this is the "Betty Botter" rhyme. It uses the words "better," "bitter" and "butter" to make the speaker trip over the word patterns.