When you hear the /ch/ sound at the end of a syllable AND it is immediately preceded by a short vowel (e.g., catch), it is spelled -tch.
There are a few cases where tch comes at the end of the first syllable in a multi-syllable word. One such word is kitchen.
tch will never come at the beginning of a word.
If there is a consonant (e.g., n or r) or vowel team (e.g. ee or ea) before the /ch/, it is spelled -ch.
Exceptions include: which, much, such, rich, and sandwich.
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