often
The word often is an antonym (opposite) of seldom, and has a silent 't'.
rarely, infrequently, seldom, occasionally
Seldom!
Frequently or Often.
The word "cancel" is the opposite of sit, in the sense of convene.
The 5 letter word that means the opposite of big and has a short vowel sound is "small."
Stand.
unsharp
It is thin.
exit
leave
sweet