simple

American Heritage® Dictionary of the English Language, Fourth Edition

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

Century Dictionary and Cyclopedia

1. Without parts, either absolutely, or of a special kind alone considered; elementary; uncompounded: as, a simple substance; a simple concept; a simple distortion.
2. Having few parts; free from complexity or complication; uninvolved; not elaborate; not modified. Hence— Rudimentary; low in the scale of organization, as an animal or a plant. Compare defs. 10, 11.
3. Without elaborate and rich ornamentation; not loaded with extrinsic details; plain; beautiful, if at all, in its essential parts and their relations.
4. Without sauce or condiment; without luxurious or unwholesome accompaniments: as, a simple diet; a simple repast.
5. Mere; pure; sheer; absolute.
6. Plain in dress, manner, or deportment; hence, making no pretense; unaffected; unassuming; unsophisticated; artless; sincere.
7. Of little value or importance; insignificant; trifling.
8. Without rank; lowly; humble; poor.
9. Deficient in the mental effects of experience and education; unlearned; unsophisticated; hence, silly; incapable of understanding a situation of affairs; easily deceived.
10. Proceeding from ignorance or folly; evidencing a lack of sense or knowledge.
11. Presenting no difficulties or obstacles; easily done, used, understood, or the like; adapted to man's natural powers of acting or thinking; plain; clear; easy: as, a simple task; a simple statement; a simple explanation.
12. In music: Single; not compound: as, a simple sound or tone.
13. Undeveloped; not complex: as, simple counterpoint, fugue, imitation, rhythm, time.
14. Not exceeding an octave; not compound: as, a simple interval, third, fifth, etc.
15. Unbroken by valves or crooks: as, a simple tube in a trumpet.
16. In botany, not formed by a union of similar parts or groups of parts: thus, a simple pistil is of one carpel; a simple leaf is of one blade; a simple stem or trunk is one not divided at the base. Compare simple umbel, below.
17. In z oöl. and anatomy: Plain; entire; not varied, complicated, or appendaged. See simple-faced.
18. Single: not compound, social, or colonial: as, the simple ascidians; the simple (not compound) eyes or ocelli of an insect.
19. Normal or usual; ordinary; not duplex: as, the simple teeth of ordinary rodents. See simple-toothed.
20. In entomology, more particularly— Formed of one lobe, joint, etc.: as, a simple maxilla; the simple capitulum or club of an antenna.
21. Not specially enlarged, dilated, robust, etc.: as, simple femora, not fitted for leaping or not like a grasshopper's.
22. Entire; not dentate, serrate, emarginate, etc.; having no special processes, etc.: as, a simple margin.
23. Not sheathed or vaginate: as, a simple aculeus or sting.
24. In chem., that has not been decomposed or separated into chemically distinct kinds of matter; elementary. See element, 3.
25. In mineralogy, homogeneous.
26. The object of a simple concept.
27. That which is not composed of different things, especially not of matter and form, but is either pure matter or pure form
28. That which is not composed of different kinds of matter, as an element.
29. Later. a dissyllabic or trisyllabic foot, with inclusion of the pyrrhic (): opposed to a compound foot in the sense of a foot compounded of these. See pyrrhic.
30. A monomial.
31. Synonyms Unmixed, elementary.
32. Unstudied, unvarnished, naïve, frank, open, straightforward.
33. Simple, Silly, Dull, shallow, stupid, preposterous, inept, trifling, frivolous. Of the italicized words, stilly is more active; the others are more passive. The simple person is not only ignorant or lacking in practical wisdom, but unconscious of his own deficiencies, so that he is peculiarly liable to be duped. That which in the simple is unconsciousness is in the silly an active self-satisfaction or conceit: the simple may be taught wisdom by hard experience; the silly have much to unlearn as well. Silliness is a form of folly. (See absurd.) He who is dull has no edge upon his mind; his mind works into a subject with the slowness with which a dull knife cuts into a piece of wood, but his mind can perhaps be gradually sharpened, so that the dull boy becomes the keen man.
34. n. That which is unmixed or uncompounded; a simple substance or constituent; an element.
35. n. A medicinal herb, or a medicine obtained from an herb: so called because each vegetable was supposed to possess its particular virtue, and therefore to constitute a simple remedy: commonly in the plural.
36. n. A person of low birth or estate: used chiefly in contrast with gentle: as, gentle and simple.
37. n. plural Foolish or silly behavior; foolishness: as, to have a fit of the simples.
38. n. A draw-loom.
39. n. A set of short dependent cords, with terminal bobs, attached to the tail of a part of the harness in a draw-loom, worked by the draw-boy.
40. n. Eccles., a simple feast.
41. To gather simples, or medicinal plants.
42. n. In French boston, or in heart solo, the winning of five tricks with a partner.
43. n. In division loo, a pool which has been put up by the dealer alone. Pools which have been contributed to by players who have been looed are double pools.
44. To make (the second or low-pressure cylinder of a compound engine) receive live steam direct from the boiler, instead of receiving its working fluid as exhaust from the first or high-pressure cylinder, as in normal series-working. This is done in starting, or occasionally with unusual overload on the engine, and the two cylinders work as two simple engines.

Wiktionary

1. adj. Uncomplicated; taken by itself, with nothing added.
2. adj. Without ornamentation; plain.
3. adj. Free from duplicity; guileless, innocent, straightforward.
4. adj. Undistinguished in social condition; of no special rank.
5. adj. Trivial; insignificant.
6. adj. Feeble-minded; foolish.
7. adj. chemistry Consisting of one single substance; uncompounded.
8. adj. mathematics Of a group: having no normal subgroup.
9. adj. botany Not compound, but possibly lobed.
10. n. medicine A preparation made from one plant, as opposed to something made from more than one plant.
11. n. logic A simple or atomic proposition
12. v. transitive, intransitive, archaic To gather simples, ie, medicinal herbs.

GNU Webster's 1913

1. adj. Single; not complex; not infolded or entangled; uncombined; not compounded; not blended with something else; not complicated
2. adj. Plain; unadorned.
3. adj. Mere; not other than; being only.
4. adj. Not given to artifice, stratagem, or duplicity; undesigning; sincere; true.
5. adj. Artless in manner; unaffected; unconstrained; natural; inartificial;; straightforward.
6. adj. Direct; clear; intelligible; not abstruse or enigmatical.
7. adj. Weak in intellect; not wise or sagacious; of but moderate understanding or attainments; hence, foolish; silly.
8. adj. Not luxurious; without much variety; plain.
9. adj. Humble; lowly; undistinguished.
10. adj. (BOt.) Without subdivisions; entire.
11. adj. (Chem.) Not capable of being decomposed into anything more simple or ultimate by any means at present known; elementary; thus, atoms are regarded as simple bodies. Cf. Ultimate, a.
12. adj. (Min.) Homogenous.
13. adj. (Zoöl.) Consisting of a single individual or zooid.
14. n. Something not mixed or compounded.
15. n. (Med.) A medicinal plant; -- so called because each vegetable was supposed to possess its particular virtue, and therefore to constitute a simple remedy.
16. n. A drawloom.
17. n. A part of the apparatus for raising the heddles of a drawloom.
18. n. (R. C. Ch.) A feast which is not a double or a semidouble.
19. v. To gather simples, or medicinal plants.

WordNet 3.0

1. n. a person lacking intelligence or common sense
2. adj. apart from anything else; without additions or modifications
3. adj. exhibiting childlike simplicity and credulity
4. adj. lacking mental capacity and subtlety
5. n. any herbaceous plant having medicinal properties
6. adj. having few parts; not complex or complicated or involved
7. adj. unornamented.
8. adj. (botany) of leaf shapes; of leaves having no divisions or subdivisions
9. adj. easy and not involved or complicated