I was studying for my exam and I came across something called elision. So my question is… Can “often” be considered an elision? Because of the silent t? Or am I just not getting the concept of elision?
It depends on the context.
"often" is an example of the diachronic elision of "t"
Historically, the word "often" started out with a /t/ sound in the pronunciation, and it lost it. So we can say that the loss of /t/ in "often" is an example of elision from a diachronic perspective.
"often" could be argued to be an example of synchronic elision of "t", but that’s disputable, & so probably not the best example for you to give of a synchronic elision process
It’s harder to make the case that the t-less pronunciation of "often" is an example of elision from a synchronic perspective, although it can be done (and I expect it has, although I’m not familiar with the relevant linguistics literature). The strongest argument in favor is probably not the spelling, but the existence of the related word "oft", where the phoneme /t/ is still present for modern-day speakers. However, "often" is is actally a much more frequent word than "oft", so it doesn’t seem obvious that the former should be analyzed as synchronically derived from the latter. But as noted in the comments, there are words like "soften", from which we could make a stronger case for the existence of a synchronic process of /t/ elision in present-day English in words that would otherwise end in /ftən/.
Even with "soften" and the "-sten" and "-stle" and words, however, there just aren’t that many examples of this kind of /t/-elision as an apparently synchronic process.
And there do seem to be words that end in /ftən/ with no elision of the /t/, such as chieftain (for speakers who can merge weak vowels before /n/ in unstressed final syllables) and the proper name Crofton, which ends in /ftən/.
It’s possible to come up with ways to account for exceptions like this in the context of a synchronic elision rule. For example, we might say the elision only occurs in words derived from morphemes ending in /ft/, so "chieftain" does not experience elision because its morphological structure is "chief + tain" rather than "chieft + ain", and "Crofton" does not experience elision because it is morphologically simple. (Or, as Janus Bahs Jacquet points out in the comments, "Crofton" could be analyzed as a cranberry-morpheme "Crof" +
a place-name suffix "-ton"; this seems to match with some analysis I vaguely remember reading that explained the lack of elision of /t/ in "-ston" proper nouns like "Boston" and "Aston" the same way. There are other types of /stən/ proper nouns for which such an analysis seems more far-fetched, though, like "Austen/Austin" (for speakers with the weak vowel merger), "Kristen" and "Kirsten".)
But the thing is, it’s not really clear if the limited amount of evidence for it justifies the rule in the first place. An answer I got to a question I asked recently on Linguistics SE, "What are current perspectives on analyzing word-final /i/ in English words like “potency” as synchronically derived from /j/?", indicates that many phonologists aren’t particularly convinced that minor alternations between related words like this are best explained by postulating the existence of synchronic morphophonological rules.