Example sentences
dà大jiā家hǎo好！
Hello everyone!
dà大jiā家dōu都lái来le了。
Everyone has come.
About this word
大 is "big" and 家 is "household", so 大家 is "the whole household", which is how Chinese says "everyone". It normally includes the speaker: 我们大家一起照张相 is "let's all take a photo together", and 大家 is the standard way to open a speech or a group message. Contrast 他们, which leaves the speaker out. It also attaches to nouns: 大家好, "hello everyone", and 大家的事情, "everybody's business".
The story behind the character
大
A person standing face-on, arms spread wide. That's 大. The ancients figured a human with arms open was the biggest, most heaven-and-earth-filling thing there is. Xu Shen wrote 天大，地大，人亦大. Heaven is big, earth is big, so is a person. So 大 started as a picture, not an adjective.
家
家 literally means a pig under a roof. 宀 is the roof, 豕 is the pig. Not a pet, but your livelihood. In the earliest writing they drew it straight: a roof, a pig underneath. For ancient people, if you could keep a pig under your roof, you were settled. Every time you write this character, you're drawing a house with a pig in it.