Intelligible means able to be understood. When someone speaks in an intelligible way, their words come through clearly enough that listeners can grasp what they mean. A teacher writing intelligible notes on the board makes letters and words clear enough for students to read and comprehend.

The opposite of intelligible is unintelligible, which describes something so unclear or garbled that you can't make sense of it. If your friend mumbles with their mouth full of food, their speech becomes unintelligible. If you write so messily that even you can't read your own handwriting later, your notes are unintelligible.

The word often appears when clarity matters most. Scientists work to make complex research intelligible to the public. An announcement over a loudspeaker needs to be intelligible, or there's no point in making it at all. When you're giving a presentation, speaking at an intelligible pace and volume ensures your audience can follow your ideas.

Notice that intelligible doesn't mean simple. A physics lecture might be perfectly intelligible (every word clear and understandable) but still difficult to grasp because the concepts themselves are challenging. Intelligibility is about clarity of communication, not ease of understanding.