Here’s how we use those words in the US: Track (noun): a thing constructed to be walked on or used for transport. A train track, subway track, racecar track; the sport “track and field” is when runners compete in a 500m sprint or 4x100 relay race. Track can also mean footprints left by an animal. Trail (noun): also a thing to be walked on, but it occurs in nature, not something constructed with man-made materials. You walk on a trail through the woods. Track (verb): to follow and search for something by details Trail (verb): to follow directly behind something A common idiom is to “keep track” of something, or to be aware of or remember something. Example sentences: - She dropped her phone on the subway track and it was destroyed a minute later when the train arrived. - The athletes ran around the track inside the stadium. - I saw wolf tracks in the snow; the paw prints were much bigger than my dog’s. - The hiking trail to the lake is 5 km long. - We read a book about the infamous “trail of tears,” when 60,000 American Indians were forced to leave their native land by foot. - He tracked the cat for 30 minutes, and eventually found where the kittens were hiding. - The baby ducklings trailed behind their mother as they walked to the pond. - My colleague has 10 grandchildren and I can’t keep track of their names.

"A track" means pretty much the same thing as "a trail" but they have subtle potential differences that most people wouldn't bother mentioning here: * A Track has subtle implication of physical signs (tracks) to follow. * A Trail has subtle implication of it being a journey that leaves signs (trails) behind or that some people find harder than others (thus, they trail behind the other people) "To track" means something quite different to (but related to) the verb "to trail": * To Track = To find someone or something, ie, "to track them down", by following the tracks they've created, ie, any signs of their journey, and hoping to catch them up or find their destination. * To trail behind = To be slower than other people, when following the same trail or course as them at the same time.