The main difference between Acre and Hectare is that the Acre is a unit of area and Hectare is a metric unit of area.
The acre is a unit of land area used in the imperial and US customary systems. It is traditionally defined as the area of one chain by one furlong (66 by 660 feet), which is exactly equal to 10 square chains, 1⁄640 of a square mile, or 43,560 square feet, and approximately 4,047 m2, or about 40% of a hectare. The acre is a statute measure in the United States and was formerly one in the United Kingdom and almost all countries of the former British Empire, although informal use continues. The international symbol of the acre is ac. In the United States both the international acre and the US survey acre are in use, but they differ by only two parts per million: see below. The most common use of the acre is to measure tracts of land. The acre, based upon the International yard and pound agreement of 1959, is defined as exactly 4,046.8564224 square metres. Traditionally, in the Middle Ages, an acre was defined as the area of land that could be ploughed in one day by a yoke of oxen.
The hectare (; SI symbol: ha) is an SI accepted metric system unit of area equal to a square with 100 metre sides, or 10,000 m2, and is primarily used in the measurement of land. There are 100 hectares in one square kilometre. An acre is about 0.405 hectare and one hectare contains about 2.47 acres. In 1795, when the metric system was introduced, the "are" was defined as 100 square metres and the hectare ("hecto-" + "are") was thus 100 "ares" or 1⁄100 km2. When the metric system was further rationalised in 1960, resulting in the International System of Units (SI), the are was not included as a recognised unit. The hectare, however, remains as a non-SI unit accepted for use with the SI units, mentioned in Section 4.1 of the SI Brochure as a unit whose use is "expected to continue indefinitely".The name was coined in French, from the Latin ārea.
From Middle English acre, aker, from Old English æcer (“a field, land, that which is sown, sown land, cultivated land; a definite quantity of land, land which a yoke of oxen could plough in a day, an acre, a certain quantity of land, strip of plough-land; crop”), from Proto-Germanic *akraz (“field”), from Proto-Indo-European *h₂éǵros (“field”). Cognate with Scots acre, aker, acker (“acre, field, arable land”), North Frisian ecir (“field, a measure of land”), West Frisian eker (“field”), Dutch akker (“field”), German Acker (“field, acre”), Norwegian åker (“field”) and Swedish åker (“field”), Icelandic akur (“field”), Latin ager (“land, field, acre, countryside”), Ancient Greek ἀγρός (agrós, “field”), Sanskrit अज्र (ájra, “field, plain”). Related to acorn.
acre (plural acres)
Borrowed from French hectare, formed from Ancient Greek ἑκατόν (hekatón, “hundred”) + are.
hectare (plural hectares)