| Term |
Description |
| ODN |
Ordnance Datum Newlyn the standard reference level for OS maps throughout the UK. |
| Offshore |
The zone beyond the nearshore zone where sediment motion induced by waves alone effectively ceases. |
| Order of magnitude |
Within a factor of ten; 1 x 101 = 10, 1 x 102 = 100, 1 x 103 = 1000 |
| Organism |
Any living animal or plant; anything capable of carrying on life processes. |
| OS |
Ordnance Survey |
| Osmosis |
Diffusion of a solution through a semi-permeable membrane into a more concentrated solution, tending to equalise the concentrations on both sides of the membrane. |
| OSPAR |
The Convention for the Protection of the Marine Environment of the North-East Atlantic |
| Overtide |
A harmonic tidal (or tidal current) constituent with a speed that is an exact multiple of the speed of one of the fundamental constituents derived from the development of the tide-producing force. The presence of overtides is usually attributed to shallow water conditions. |
| Oxidation |
The combination of oxygen with a substance, or the removal of hydrogen from it or, more generally, any reaction in which an atom loses electrons. |
| Oxygenation |
The process of adding dissolved oxygen to a solution. |
