cloud /klaʊd/ (noun) a grey or white mass that floats in the sky, made of very small drops of water Example: The sun went behind a cloud
sun /sʌn/ (noun) the star that shines in the sky during the day and gives the earth heat and light Example: The sun was shining and birds were singing
sky /skaɪ/ (noun) the space above the earth that you can see when you look up, where clouds and the sun, moon and stars appear Example: The sky suddenly went dark and it started to rain
star /stɑːr/ (noun) a large ball of burning gas in space that we see as a point of light in the sky at night Example: Sirius is the brightest star in the sky.
moon /muːn/ (noun) the round object that moves around the earth once every 27½ days and shines at night by light reflected from the sun Example: There is a bright moon tonight.