abreast

adverb, adjective

1. side by side; beside each other in a line: They walked two abreast down the street.
2. equal to or alongside in progress, attainment, or awareness (usually followed by of or with): to keep abreast of scientific developments; keeping abreast with the times.

adjective (postpositive)

1. alongside each other and facing in the same direction
2. (foll by of or with) up to date (with); fully conversant (with)

adv.

mid-15c., on brest, from a- (1) + breast (n.); the notion is of “with breasts in line.” To keep abreast in figurative sense of “stay up-to-date” is from 1650s.