The other day I listened to a radio interview in which the subject continually pronounced the word tentative without one of its ts.
Tentative has three ts: ten-ta-tive (not ten-a-tive).
Another “t word” that often has its medial t messed with is tenterhook. It’s an old word derived from cloth-making, but it remains current in the expression “to be on tenterhooks,” i.e., to be in a state of painful suspense. I’ve heard people say “tenderhooks.”
Tentative derives from Latin tentatus, a form of the verb tentare, “to feel, to try.” It’s another form of temptare, “to feel, to try, to test.” which gives us the English word temptation.
A tenter was a wooden framework for stretching cloth. It derives from Latin tentus, “stretched.” A “tenter hook” held the cloth on the tenter.
Some will argue that these pronunciations are merely differences of region or dialect. Whatever the cause, pronouncing them that way leads to misspelling them and misspelled words damage the writer’s credibility.