Haplology

Haplology is the loss of one of two similar or identical syllables in adjacent or nearby parts of a word or phrase. It can occur during historical sound change or in speech production.

Dissimilation: A sound change in which one of two similar sounds becomes less like the other. Haplology is a syllable-level form of dissimilation: similarity prompts one repeated unit to disappear.
February: The second month of the Gregorian calendar, whose name descends from Latin Februarius. The common pronunciation with one fewer rhotic sequence is often cited as a case of haplology.
Historical linguistics: The study of how languages change and how related languages develop from common ancestors. Haplology is a recurring sound change reconstructed from differences among historical forms.
Synaloepha: The joining or elision of vowels across a word boundary, especially in poetry. Synaloepha concerns adjacent vowels across words, not the loss of one similar syllable.
Syncope: The loss of a sound or syllable from the middle of a word. Syncope removes medial material without requiring a similar neighboring syllable.
Library: An institution or collection that provides access to books and other information resources. Some pronunciations reduce the sequence of similar syllables in this word.
Sound change: A systematic change in how a language's sounds are pronounced over time. Historical haplology is one specific kind of sound change.
Apheresis: The loss of a sound or syllable from the beginning of a word. Apheresis is defined by position at the word's start, not by repetition.
Elision: The omission of a sound or syllable in pronunciation, often at a word boundary. Elision also deletes spoken material, but usually describes pronunciation rather than a historical syllable pattern.
Probably: An adverb expressing that something is likely but not certain. Casual pronunciations often reduce the similar syllables in probably to a shorter form.

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EpenthesisCompared with: It is a specific kind of reduction that contrasts with sound insertion.