Bulan

Bulan is a word used in Malay and Indonesian that has two related meanings: the Moon, Earth’s natural satellite, and a month in a calendar. The intended meaning is usually clear from context, for example bulan Januari refers to January, while bulan purnama or bulan sabit refers to moon phases or the crescent. The term also appears in set phrases such as bulan madu (honeymoon), illustrating a metaphorical use of the word.

In astronomy, the Moon orbits Earth at about 384,400 kilometers on average and is tidally locked, presenting the same face to our planet. A sidereal month, the orbital period relative to the distant stars, is about 27.3 days, while a synodic month—the cycle from one new moon to the next—lasts about 29.53 days. The Moon’s phases—new moon, first quarter, full moon, and last quarter—result from the changing angle between the Sun, Moon, and Earth. The Moon’s gravity drives tides and influences the Earth’s rotation over long timescales.

Culturally and linguistically, lunar months are significant in many traditions. The Islamic Hijri calendar is based on lunar months, and months begin with sightings of the crescent moon. In Malay-speaking regions, bulan serves both as Moon and as a calendar month, reflecting the language’s dual meaning. The word bulan has cognates in other Austronesian languages; for example, Tagalog buwan means both moon and month, illustrating a shared linguistic heritage.