Natural (adjective)

1. Existing in or caused by nature; not made or caused by humankind.
2. In accordance with the normal functioning of a living organism or ecosystem.
3. In accordance with the usual course of events; not forced or artificial.
4. Having or showing the qualities or abilities that are typical of a particular person, group, or thing.

Origin:

Late middle english: from old french naturel, from latin naturalis, from natura "nature".

Examples:

1. The natural beauty of the landscape was breathtaking.
2. The natural progression of the disease.
3. It's natural for a baby to cry.
4. He had a natural talent for music.
5. The natural resources of the country are being depleted.