improvement

Behind every sense of the word stands Anglo-Norman emprouwement, though English now reads it simply as improve plus -ment. Here it names the work of bettering, not the result, which belongs to the bettered state. Improvement of points to what is being bettered (the improvement of the roads). Improvement in points to where the gain shows, as when Hugh Blair calls exercise the chief source of improvement in all our faculties.

Older usage let improvement mean plain growth, with no promise that the thing growing was good. Robert South preaches on vices that "receive improvement by prosperity," and he means they swell, not that they mend. When this sense turns up in early prose, read it as increase. Modern writing usually leans toward the approving meaning of the bettered state.

A property word that usually travels in the plural: improvements are the buildings, fences, drains and cleared ground added to land, often paired with on, as in improvements on the premises. Unlike the bettered thing, an improvement here is something new placed on the land. A fence counts even though nothing old was made better.

Patent law treats an improvement as an invention in its own right. It may be patentable even though it depends on the earlier machine, manufacture or composition it refines. That dependence is the practical point: an improvement builds on an existing invention rather than replacing it. Everyday speech uses the word for any change for the better, but here it names a protectable modification.

A preacher's word from the age of Tillotson and Samuel Clarke. To make improvement of a doctrine was to draw out its practical use, the part of a sermon that turned exposition into conduct. Tillotson promises "some improvement of this doctrine" in 1681, and Clarke speaks of the good improvement of one's reason. In older prose it means using something well, not making it better, and that is easy for a modern reader to miss.