natural sign

adjective

1. of or arising from nature; in accordance with what is found or expected in nature
2. produced or existing in nature; not artificial or manufactured
3. dealing with nature as an object of study: a natural science
4. in a state provided by nature, without man-made changes; wild; uncultivated
5. of the real or physical world as distinguished from a spiritual, intellectual, or imaginary world
6. 1. present by virtue of nature; innate; not acquired
   2. having certain qualities, abilities, etc. innately: a natural comedian
7. innately felt to be right; based on instinctive moral feeling: natural rights
8. true to nature; lifelike: a natural likeness
9. normal or usual; in the ordinary course of events: a natural outcome
10. customarily expected or accepted: a natural courtesy
11. free from affectation or artificiality; at ease: a natural smile
12. without a legal relationship; specif.,
    1. illegitimate: a natural child
    2. relating biologically rather than by adoption: natural parents
13. with little or no processing, artificial ingredients or preservatives: natural food
14. off-white, light-beige, etc.
15. resulting from age, disease, etc. rather than an accident, violence, etc.: a natural death, death from natural causes
16. Biol. designating or of a system of classification based on complete structure and characteristics
17. Math.
    1. designating or of an integer or any number referred to 1 as the base
    2. designating or of an actual number as distinguished from its logarithm: a natural sine, cosine, etc.
18. Music
    1. without flats or sharps, as the key of C major
    2. modified in pitch by the sign (♮)
    3. neither sharped nor flatted

Origin: OFr < L naturalis, by birth, according to nature

noun

1. a person without normal intelligence; fool; idiot
2. Informal a person who is or seems to be naturally expert
3. ☆ Informal a thing that is, or promises to be, immediately successful
4. ☆ Informal a winning roll of 7 or 11 on a first throw in craps
5. Music
   1. a sign (♮) used to remove the effect of a preceding sharp or flat within the measure in which it occurs
      in full, natural sign
   2. the note so changed
   3. a white key on a piano