under way, underway, under weigh

The Canadian preference is to write this expression as two words, under way.

• We expect the symposium to get under way around noon.

When the expression is used as an adjective, it is spelled as one word in the United States.

• Once the race is underway, no one will be allowed to cross the highway.

The variant spelling under weigh originated through a mistaken association between the nautical phrase “under way” and the verb “weigh,” as in “weigh anchor.” This variant is accepted as an alternate spelling.

• A ship is under weigh once it weighs—pulls up—its anchor and begins moving.