The internal diameter of a tube, conductor, or coupling, as distinguished from its OD (Outside Diameter). Fire hose sizes are classified by a nominal internal diameter.

The ratio between the surface area of an object, such as a fuel particle, to its volume. The smaller the particle, the more quickly it can become wet, dry out, or become heated to combustion temperature during a fire.

A plan for responding to a variety of potential hazards.

Use of two or more fire pumps to move water a distance which would require excessive pressures in order to overcome friction loss if only one pump were employed at the source.

Green leaves and succulents, uncured vegetation which bends and curls inwards towards the heat source due to desiccation. One of the 11 NWCG categories of fire pattern indicator.

Development of new aboveground plants from surviving plant parts, such as by sprouting from a root crown or rhizomes. Even if plants form their own root system, they are still genetically the same as the parent plant.

Documented, satisfactory performance in a specified position needed to qualify for another (usually higher level) position. Required experience cannot be challenged.

A combustible or non-combustible object that displays differential damage or deposits on opposing sides due to the passage of the fire and indicates the direction of fire progression at that location.  One of the 11 NWCG categories of fire pattern indicators.

Setting fire inside a control line to consume fuel between the edge of the fire and the control line.

A fire set along the inner edge of a fireline to consume the fuel in the path of a wildfire or change the direction of force of the fire's convection column.