The
Use it when both speakers know what you mean, or when the thing is unique.
Rule
Use the when the thing is already known, already mentioned, or specific in the situation. Also use it with unique things such as the sun.
Examples
- The sun / the moon (unique things)
- I bought a phone. The phone is great. (already mentioned)
- Close the door. (the specific door here)
- the kitchen, the door (a specific place or thing)
Notes
- No article: Dogs are friendly. (plural in general)
- No article: Water is important. (uncountable in general)
- No article: I live in Kyiv. (names of people and cities)