Apt to is a phrase used to describe someone or something that has a tendency or inclination to do or be a certain way. Synonyms for apt to include likely, prone, predisposed, disposed, inclined, given, expected, liable, and susceptible. These words can all be used to convey the same meaning as apt to, but with slight variations in connotation and emphasis. Likely suggests a high probability, predisposed suggests a natural inclination, and susceptible suggests vulnerability to outside influences. Regardless of which synonym you choose, the message remains the same: someone or something is prone to a certain behavior or outcome.