What is the most obvious difference between apes and monkeys?

Apes and monkeys are primates that have evolved different physical and mental characteristics throughout time to respond to different needs and environments. For example, most monkeys have an easily visible tail, but no apes do.

Monkeys and apes are clearly different, despite common terminology often using the words as interchangeable. One thing both share in common, however, is a high level of endangerment and extinction threats.

The greatest differences between these primates are believed to lie in intelligence levels. Monkeys are far more similar to the primitive prosimians in brain capacity and capabilities. Apes are closer to their human counterparts, able to learn forms of sign language, use tools, and display problem solving skills.