Other forms: hastened, hastening, hastens
To hasten is to hurry, or to make something happen sooner. Speed, applied to yourself or to events.
The transitive use is the commoner one in writing, so poor weather hastened the decision means it brought it forward. The reflexive-sounding use appears in fixed phrases, and I hasten to add is a set expression for quickly correcting a possible misunderstanding, which is very nearly the only place many people meet the word. It is formal throughout. Hasty and haste belong to it, and haste makes waste is the proverb about hurrying badly.
Middle English
hasten
English
haste
English, today
hasten
Originally intransitive, from haste + en. haste Blend of Middle English hasten, (compare Dutch haasten, German hasten, Danish haste, Swedish hasta (“to hasten, rush”)) and Middle English hast (“haste”), from Old French haste (whence French - hâte), from Old Frankish haifsti (“violence”), from Proto-Germanic haifstiz (“struggle, conflict”), from Proto-Indo-European ḱeyp- (“to ridicule, mock, anger”). Akin to Old Frisian hāst, hāste (“haste”), Old English hǣst (“violence”), Old English hǣste (“violent, impetuous, vehement”), Old Norse heift//heipt (“feud”), Gothic 𐌷𐌰𐌹𐍆𐍃𐍄𐍃 (“rivalry”). Cognate with German heftig (“vehement”) and Danish heftig (“vehement”).
Etymology from Wiktionary, CC BY-SA