These words refer to the heightening of something in scale, as pressure, tension, pay or military activity. Escalate is a new word for such buildups; it can imply either a gradual process or a series of sudden or surprise spurts. It is most often used for rising prices and pay rates or for military activity: factors causing the cost of living to escalate during the third quarter; a built-in clause that would escalate their weekly pay to keep pace with rising prices; They escalated the war by mining the enemy’s harbours. As in the second example, the word can suggest two scales rising reciprocally, or one of these rising in response or anticipation of the other: any aggressive act that would escalate the war to a new level of intensity on both sides. The word’s faddish appeal can be seen in the way it replaces simpler words in a wide range of contexts: We escalated our efforts to get the weekender built before summer.

Step up , by contrast, might more logically suggest a series of spurts with level intervals between them: businesses that must step up production during periods of seasonal demand. This notion is by no means held to, and the word can be used for any single or even gradual act of heightening: immigration quotas that were stepped up by the new policy; directors who inevitably step up their pressure on the actors as opening night approaches.

Increase is a much more general word than the foregoing and can often replace either to advantage, with a possible gain in simplicity and clarity. While the word can apply to any build-up, its particular point is sometimes to indicate a gain in amount.

• The number of people browsing in the bookshop increases sharply during lunch hour.

Intensify is of comparable generality, but it is often directed towards a heightening of pressure, tension or insistence: floods that intensified the force with which the river battered against the weakening levees; the introduction of a plot device to intensify the film’s suspense; arrogant behaviour that only caused the union leaders to intensify their demands.