What is simple? What is simple? Having or composed of only one thing, element, or part. See Synonyms at pure.Not involved or complicated; easy: a simple task. See Synonyms at easy.Being without additions or modifications; mere: a simple "yes” or "no.” Having little or no ornamentation; not embellished or adorned: a simple dress. Not elaborate, elegant, or luxurious. See Synonyms at plain.Unassuming or unpretentious; not affected.Having or manifesting little sense or intelligence.Uneducated; ignorant.Unworldly or unsophisticated. See Synonyms at naive.Not guileful or deceitful; sincere.Humble or lowly in condition or rank: a simple woodcutter. Ordinary or common: a simple head cold. Being a fundamental or rudimentary element; basic.Not important or significant; trivial.Biology Having no divisions or branches; not compound: a simple leaf; a simple eye or lens. Music Being without figuration or elaboration: a simple tone. A single component of a complex, especially one that is unanalyzable.A fool; a simpleton.A person of humble birth or condition.A medicinal plant or the medicine obtained from it.