In linguistics, TCOM (always written as uppercase T plus uppercase COM in subscript) is an abbreviation for the time of completion, a secondary temporal reference in establishing tense.
Grammatical tense represents the contrast between two measurements along the timeline of an utterance, with one of those measurements being the time of utterance TUTT (the time at which the actual utterance is made). TUTT is always the primary point of reference for tense. There are three additional references to which TUTT can be contrasted: TAST — the time of assertion, TCOM — the time of completion, and TEVL — the time of evaluation; these are secondary references. The type used for the secondary reference is determined by aspect and type of utterance.
TCOM is the point in time at which a verb is completed. TCOM is used with perfected forms. In perfected non-durational aspects it represents the time by which a verb is finished, as in English “I have eaten dinner.” In perfected durational aspects it represents either the time at which a verb is finished, or more normally, a time up to which the verb is completed (but that it may continue beyond); this meaning of interrupting the verb is the more standard use of this form and allows the duration of the verb to be measured up to a given point (TCOM). Consider “I had been eating for 2 hours by 7pm,” in which an action (eating) has a duration, of which two hours of it is completed as of 7pm.