A lexical function is a group of words that perform a specific job in a sentence. It's like having a team of helpers who always do a certain task together. For example, the words "make up" often work together in a sentence to mean "create" or "invent." So, when we see the words "make up" together, we know what job they're doing in the sentence.
Another example of a lexical function is the words "take off." When these words are together, they often mean "remove" or "depart," like when someone takes off their coat or takes off in an airplane. So, if we see the words "take off" together in a sentence, we know that they're working together to do a certain job.
Overall, a lexical function is just a group of words that often work together to perform a specific job in a sentence. And just like how we rely on certain helpers like a plumber or a doctor for specific tasks, we rely on lexical functions to help us understand the meaning of a sentence.