period of ten years. Periods of 10 years.

Series of letters or numbers needed to open a lock.

needing much effort or skill to accomplish, deal with, or understand.

tumour of melanin-forming cells.

To know the meaning of language, what someone says.

Treatment of diseases using chemicals.

having acquired much knowledge through study. To get knowledge or skills by study or experience.

change something radically or fundamentally.

Not of the same kind; unlike other things.

Therapy designed to produce immunity to a disease or to enhance resistance by the immune system.

state or fact of continuing to live or exist.

treatment intended to relieve or heal disorder.

officially agreed or accepted as satisfactory. To have a positive opinion of someone or something.

Concerning academic study of the physical world.

Relating to biology; biological.. another term for biological (noun).