Last
Stop
Terminate
Destroy
Destruct
The word you're looking for is "teapot." It starts with a T, has another T in the middle, and ends with a T. So, there you have it, a word with T at the beginning, T inside, and T at the end. Now go impress someone with that fun fact!
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Another word for end is finish.
tilt
thought
teapot
Complete is another word for finish.
Another word for "in the end of the book" could be "ultimately" or "finally."
Some words that mean to end: stop. cease. refrain. avoid.
Another word for conclude is to finish or to end.
talking sh*t
Internet is a word beginning with I and ending with T.