The term 'effective use of lang' can be summarized as the ability to use language in a way that is effective and meaningful. Rhet, which is a four letter word, is a form of communication that uses language to persuade or influence an audience. It is often used in public speaking, writing, and other forms of communication. Effective use of language involves using words and phrases that are appropriate for the situation and audience, as well as being able to communicate ideas clearly and concisely.