Other forms: touring, toured, tours
A tour is a journey visiting several places, or a run of performances in different towns. A walking tour, a guided tour, the band is on tour.
On tour takes no article and is the fixed phrase for performers and sports teams. A tour of a building is a visit with somebody showing you round, and that is what a guided tour means. In the army, a tour of duty is a fixed period of service in one place. Note tourism and tourist, both from the same word, and that tour operator and tour guide are different jobs — one sells the trip and the other walks it with you.
1nountourA run of performances in different places.
“The tour takes in fourteen cities.”
2nounjourneyA journey visiting several places.
“They did a walking tour of the Dales.”
3nounroundA visit round a building or site with a guide.
“A guide took us on a tour of the old castle.”
4verbtravelTo travel around a place or perform in several places.
“They toured for two years without a break.”
Too few real examples of this word to estimate which sense is commonest.
tour is a journey or run of visits.
Old French tour meant a turn or a circuit, from Latin tornus, a lathe. A tour is a going round and coming back, which is why a one-way journey is not one.
Old French
tour
English, today
tour
From Old French tour, from torner. From Old French tour, tourn, from the verb torner, tourner.
Etymology from Wiktionary, CC BY-SA