If you are doubtful about contractions, especially in writing, check out this story.
Words that combine two or more words into a shortened form, typically with an apostrophe, are called contractions.
E.g., the contraction of "I am" is "I'm".
Usually, small words (not, is/are), pronouns (I, he/she/it, they), and modal verbs (can, will, might, must, should, etc.) are used for contractions.
Even though all contraction has a distinct spelling, sometimes two distinct contractions, such "I would" and "I had", might have the same spelling (I'd).
Since contractions are considered to be informal, it is not used for formal writing or conversation.
It is best not to use double contractions, like "mustn't've", etc., in writing as it is too weird for any kind of writing.
While using contractions with nouns (e.g., "My friends're on the way.) is common in speaking, it is typically avoided for writing, as it is too informal.
Some contractions, like "ain't", "y'all" are specific to certain regions.
As a result, everyone may not understand it & it is best to avoid using them.
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