An informal type of contraction occurs frequently in speech and writing, in which a syllable is substituted by an apostrophe and/or other mode of elision, e.g., can't for "cannot", won't for "will not". Such contractions are often either negations with not or combinations of pronouns with auxiliary verbs, e.g., I'll for "I will". At least one study has sought to analyze the category of negative informal contractions as the attachment of an inflectional suffix.
Full form Contracted Notes
let us let's
does very informal
has American English only contracts forms of have when used as auxiliaries
of o'– used mostly in o'clock
it 't– Archaic, except in uses such as 't's (that is); "'t's what I said!"
you –ya, –ja, –cha Very informal in writing
— –'em Contracted from hem, but used for modern them
Informal speech sometimes allows multiple contracted forms to pile up, producing constructions like wouldn't've for "would not have". Another stereotypically informal contraction is ain't, for "am not" or "is not".