single word requests - Describing the phonetic interaction between the F and the T in often

In the word often, the labiodental non-sibilant fricative f precedes the alveolar stop t, which is then followed by the vowel e. The Oxford Dictionaries Online offers two accepted pronunciations:

/ˈɒf(ə)n/ /ˈɒft(ə)n/

I would like to describe the phonetic interaction between the f and the t in the pronunciation
/ˈɒf(ə)n/. The sole pronunciation of the archaic oft, leads me to consider that the vowel plays a significant role in silencing the t. Though I doubt it is the standard terminology, I would tend to describe it in laymen's terms with the word picture underlying fricative:

the fricative rubs out the stop in concert with the vowel

If that seems like an acceptable description, I would be content with it, but I would like to know if there is a more precise professional description of that phonetic effect.

Answer

I think the term you are looking for is assimilation:

• Assimilation has a very precise meaning when it’s related to studies of languages. Is a common phonological process bye which the phonetics of a speech segment becomes more like another segment in a word. In other words it’s when a letter (sound) is influenced by the letter (sound) before or after it so that it changes its sound and/or spelling. The word assimilation it self it’s said to be assimilated; it is derived from the latin prefix ad- meaning to and simil- meaning like but, instead of being adsimilated, it has the easier pronunciation of assimilated.

(phonetics-and-phonology)

Often: as explained in the following extract by James W. Bright:

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  “often,” the word can be properly pronounced either with or without a “t” sound. The “t” had long been silent but it came back to life in the 19th century with the rise of literacy, when people seemed to feel that each letter in a word should be sounded.

  
  


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  The article, “On ‘Silent T’ in English,” by James W. Bright, appeared in the journal Modern Language Notes in January 1886.

  
  


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  As Bright explains, the “t” in these words is an acoustically “explosive” one, and to sound it after an “s” or an “f”—both of which expend “considerable breath”—is “especially difficult and obscure.” Consequently the “t” sound is assimilated into its surroundings and becomes silent.

  
  


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  However, the “t” sound persists in some other words spelled with “-stl” and “-ftl,” like “lastly,” “justly,” “mostly,” “shiftless,” “boastless,” and others.

  
  


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  Bright explains that such words “are, with most persons familiar with their use, conscious compounds; as they become popular words, and therefore subject to unstudied pronunciation, they conform to the regular rule. It is only after administered caution that we learn to make t audible in wristband.”

  
  

(grammarphobia.com)