brachi- or brachio-comb. form

• one's star is rising
• one-step
• one-time
• one-to-one
• one-track
• one-two
• one up
• one-upmanship
• one-way
• one way and another
• one way or the other
• one-woman
• one-world
• on file
• on fire
• on firm ground
• on first-name terms
• on/for sale
• ongoing
• on hand
• on her beam-ends
• on high
• on hold
• on horseback
• on/hot on the heels of