Other forms: slower, slowed, slowing, slows, slowest
Slow means moving or happening with little speed. A slow train, slow progress, slow down. It is the plain opposite of fast and one of the first adjectives anybody learns.
The adverb is the difficulty. Slowly is the standard adverb — drive slowly — but slow is also used adverbially in fixed phrases and on road signs: go slow, drive slow. Both exist; slowly is always safe. Two other senses: a clock that is slow shows an earlier time than it should, and a person described as slow is being called unintelligent, which is unkind and best avoided. Slow down is the everyday phrasal verb and takes an object or none.
1adjectiveslowMoving or happening with little speed.~82%
“The traffic was slow all the way into town.”
2verbbecomeTo become or make less fast.~2%
“Slow down before the corner.”
3adjectiveclockOf a clock, showing an earlier time than the true one.~2%
“That clock is ten minutes slow.”
4adjectivetakingTaking a long time to happen.~14%
“Progress has been slow and expensive.”
Shares are an estimate: a language model read 17 sentences found in the wild and placed 14 of them on a sense (3 were unclear) — a count of our sample, not a measurement of English.
slow is a rate of speed.
Old English slaw meant lazy or dull rather than unhurried, and the Proto-Germanic ancestor covered blunt, sluggish and dim-witted all at once. The modern insulting sense is not a new invention — it is the oldest meaning surviving beside the newer one about speed.
Proto-Indo-European
*(s)leyH- — bad
Proto-Germanic
*slaiwaz — blunt; dull; exhausted, faint, sluggish, weak, weary; listless, torpid; dim-witted, slow; lazy, slack
Proto-West Germanic
*slaiw
Old English
slāw — lazy; inert, slow
Middle English
slaw
English, today
slow
From Middle English slaw, slow, from Old English slāw (“lazy; inert, slow”), from Proto-West Germanic slaiw, from Proto-Germanic slaiwaz (“blunt; dull; exhausted, faint, sluggish, weak, weary; listless, torpid; dim-witted, slow; lazy, slack”), possibly from Proto-Indo-European (s)leyH- (“bad”). 2 Cognate with Dutch slee, sleeuw (“cramped, stiff; blunt; sour”), Danish sløv (“blunt; dull; apathetic, lethargic, listless, sluggish, torpid; drowsy”), Icelandic sljór (“dim-witted; blunt; jaded”), Norwegian Nynorsk sljo, slø, sløv (“blunt; weak; lazy”), Swedish slö (“dull; lazy, lethargic, slow, sluggish”).
Etymology from Wiktionary, CC BY-SA