These words refer to terrain that rises or drops away sharply or that approaches the vertical. Steep , while indicating a relatively sharp inclination or a considerable departure from the horizontal, is alone among these words in indicating a gradual or steadily increasing slope, usually one that is difficult to negotiate. The word’s relativity can be seen by the fact that a grade too steep for a locomotive might be considered a gentle rise for someone on foot; terrain that was too steep for a horse to climb might not be steep enough to interest mountain climbers. Another even more subtle connotation of the word, not always present, is its special suitability for a rise viewed from below.

By comparison, abrupt , while referring to a much sharper slope, very often suggests an incline viewed from above.

• We were winded by our long climb upwards along the steep path; They were confronted by an abrupt chasm as they emerged from the forest.

This distinction does not always hold. Abrupt suggests sudden discontinuities in a terrain rather than the gradual change implicit in steep ; consequently, a sharp contrast with surrounding topography is a special point of the word; the abrupt and dramatic looming up of the huge rock out of the level plain. In a related, more common use, abrupt refers to a sudden change: an abrupt stop as they came upon the accident; an abrupt change of plans.

Like abrupt , the remaining words pertain to a nearly vertical incline. Precipitous has special relevance to an incline viewed from above. Precipitous also brings to mind suddenness or unexpectedness in referring to a nearly vertical incline that is clifflike. The unique point of this word may be its suggestion of an abrupt drop that is dangerous or perilous: a frail rope bridge over the precipitous chasm. The word can be used without this implication: looking up at the precipitous rise of lofty buildings along both sides of the street. Sheer is related to steep in suggesting an incline viewed from below, but it is more intense than steep ; sheer often refers to a nearly vertical surface that may be impossible, not merely difficult, to negotiate: the sheer face of the high wall that stood between him and his freedom. The word also has a special implication that concerns the vertical face itself, suggesting one without break, foothold or cranny: the sheer surface of the cliff where not even a blade of grass had found a place to lodge.