phosphorus

Everyday

1. (science) Phosphorus is a chemical element, a non-metal with the symbol P and atomic number 15. tree →
2. It is needed by all living things: it is in our bones, teeth and DNA, and plants need it to grow. tree →
3. Pure white phosphorus glows in the dark and catches fire by itself in air, so it is very dangerous; red phosphorus is safer and is used on matchboxes. tree →

In the lessons

In science it appears in the periodic table, in lessons on bones and healthy food (milk, fish, nuts) and in plant fertiliser (N-P-K: nitrogen, phosphorus, potassium). In history and safety, white phosphorus is a dangerous chemical used in some weapons. The word comes from Greek for "light-bringer" because it glows.

Examples

• Phosphorus is element number 15 in the periodic table. tree →
• Our bones and teeth contain calcium and phosphorus. tree →
• Farmers add phosphorus to the soil so crops grow well. tree →
• The strip on the side of a matchbox has red phosphorus in it. tree →
• White phosphorus glows faintly in the dark. tree →
• Never touch white phosphorus; it can burn your skin. tree →
• Milk, eggs and fish give us phosphorus. tree →

Note

Uncountable: say "some phosphorus", not "a phosphorus". Spelling trap: the noun ends -us (phosphorus); "phosphorous" with -ous is an adjective. Glow-in-the-dark toys usually do not contain phosphorus — they use other materials called phosphors. Symbol P, not Ph.