All of the words in your question except for "syllable."
Crumb is a one syllable word.
no word it isn't possible because if you take away one syllable from a five syllable word you get a four syllable word and there is no such thing as a "no syllable word"
Yes. It is a one syllable word.
Why Yes, "what" is a word with one syllable.
Yes, the word "the" has one syllable.
Yes, this is a one syllable word.
The word talked has one syllable.
Yes, "vase" is a one-syllable word.
No. The word 'their' has one syllable.
A one-syllable word, yes.
A one syllable word has only one syllable. A ten syllable word has ten. There are no one syllable words with ten syllables.
There is one syllable for the word what.