Okay, pay attention, take notes if necessary:
Yeah – an alternative, more casual version of “yes.” An affirmative. “Yeah, I remembered the soda.”
Yea – an Old English word, pronounced “yay.” “Yea, though I walk through the Valley of Rape and Despair . . . “
Yay – an expression of excitement. “Yay! You remembered the soda!”
Ya – an informal version of “you.” “Top of the mornin’ to ya.”
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Then – used to illustrate sequence. “I bought the soda and then I went to the party.”
Than – used to illustrate difference. “The soda cost more than the chips.”
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There – used to illustrate location. “Put the soda over there.”
Their – used to illustrate possession. “The party will be at their house.”
They’re – a contraction of “they are.” “I’m bringing the soda, they’re bringing the awesome.”
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A – indefinite article used before words that begin with a consonant sound. “Hand me a soda.”
An – indefinite article used before words that begin with a vowel sound. “It would be an honor to hand you a soda.”
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Its – possessive of “it.” Note that there is NO apostrophe. “Here is the car’s engine, and over there is its hood.”
It’s – contraction of “it is.” “It’s awesome that you brought soda.”
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There’s lots more, so I’ll do sequels. Stay tuned.
I’m sure I’ll mention “Who” and “Whom,” but I’m still working on figuring that one out.