1 Looking at the History
Humans have used the terms "ape" and "monkey" interchangeably for most of history. This happens even today, where people refer to monkeys as apes and vice versa. No matter how similar they look, there certainly are differences between the two. Before delving into the differences, we need to keep in mind that both monkeys and apes are primates.
There are over 300 species of primates on our planet. This includes human beings and other apes along with monkeys and prosimians like lemurs. Primates can be distinguished by having hand-like feet, hands, and eyes that face forward. Apart from human beings, primates are mostly agile tree-dwellers.
2 Looking at the Differences
Even though humans and lemurs are both primates, we can clearly see how different the two are. Similarly, there are many differences among the different kinds of primates. You can describe most of these differences based on their evolutionary development and physical characteristics. The easiest and probably the quickest way of differentiating an ape from a monkey is by looking at the tail. Most species of monkeys have tails while apes do not have one. Monkeys tend to be smaller than apes and even smaller brains.
Their lifespan is also shorter than apes. While moving across trees, apes use their arms for swinging from branch to branch. This is known as brachiating. Monkeys, on the other hand, run through the branches while moving across trees. The skeletal structure of a monkey is similar to that of a smaller, four-legged mammal such as a dog or cat. Baboons, capuchins, tamarins, macaques, and marmosets are some of the monkey species. The ape species include bonobos, gibbons, orangutans, chimpanzees, gorillas, and humans. (See Monkeys have entered the Stone Age Facts)
3 3. Looking at Evolution and Genes
In genetic and evolutionary terms, humans are a lot closer to the ape species than the monkeys. Humans and apes not only have similar basic body structures but are also very intelligent. The behavior of apes is also very human-like. For example, chimpanzees are known for creating simple tools and putting them to effective use. Even in terms of genetics, they are closest to us. Even though monkeys do communicate with each other, apes have more advanced language and cognitive skills.
Although they don't speak like us, they can use bodily movements and sign language for effective communication with humans. Communication also helps chimps, bonobos, and gorillas in developing complex social groups and also display certain elements of culture. Apes, like humans, can even think and solve issues in their environments. So, we people are similar to the apes in a lot more ways than one.