Tea — the beverage made from tea leaves (e.g., green tea, black tea).
朝ごはんに茶を一杯飲むのが習慣だ。
I have a cup of tea with breakfast every morning.
食後に熱い茶をもう一杯どうですか。
Would you like another cup of hot tea after the meal?
喫茶店で抹茶ラテを頼んだら、とても美味しかった。
I ordered a matcha latte at the café and it was very tasty.
The tea plant itself (Camellia sinensis).
この山では昔から茶を栽培している。
They have been cultivating tea on this mountain for a long time.
The preparation or making of tea — the act of brewing/whisking tea; can refer to tea ceremony practices.
茶の作法を習っているので、来週のお点前に参加する。
I'm learning tea ceremony etiquette, so I'll take part in next week's tea performance.
A color — brown. Often called 'chairo' (茶色), but sometimes abbreviated as 'cha' (茶).
彼は茶のコートを着ていたので、すぐに見つけられた。
He was wearing a brown coat, so I found him quickly.
カラーパレットで『茶』を選んでください（茶＝茶色）。
Please choose 'cha' on the color palette (cha = brown).
An archaic meaning: mockery or treating something lightly in a teasing way (largely obsolete; the sense survives in verbs like 茶化す).
古い文献には、相手を『茶』にする表現が見られるが、現代語では稀だ。
In old texts you can find expressions that 'make someone tea' (i.e., mock them), but this is rare in modern language.