Warm
い adjective
This is a single kanji with an い on the end, meaning you know it's probably an adjective. What's the adjective form of warm? It's warm.
Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading. You didn't learn that reading with this kanji, so here's a mnemonic to help you:
What do you say when your friend wants to get out of a warm onsen before you? "Ah… Ta-ta (あたた)!" Yeah, you're not getting out of this warm bath yet — your friend can go on ahead. You just sigh in warm, blissful comfort and wave bye: "Ah… Ta-ta!"
People often pronounce this as あったかい, especially in casual, spoken Japanese. The "correct" reading is still あたたかい though, so keep that in mind when you're trying to type the kanji or taking an important test!
母の手はいつも温かい。
My mother's hands are always warm.
温かいお茶が飲みたいなぁ。
I want to drink warm tea.
初心者なので、どうか温かい目で見守ってください。
I'm a beginner, so please go easy on me.