CHANCELLOR KOHL'S brief visit here was evidently, as these are scored, a success. As the ranking conservative politician in continental Europe, he was here to remind President Reagan that there is more than one definition of conservatism. He wanted to be sure that Mr. Reagan fully understood what his European friends and allies will want and need over the coming months.

Above all, the alliance will need some demonstration that American policy takes European interests into account. Mr. Kohl's immediate purpose here was to head off any repetition of the long and rancorous dispute over the Soviet gas pipeline last summer, following the mismanaged Versailles summit. With the next of these summit meetings at Williamsburg next month, Mr. Kohl came not only to work out an understanding on Eastern Europe, but, presumably, to try to establish a degree of harmony at least for the month of May on these discussions generally.

There are important differences between the conservatism of the Reagan White House and that of German Christian Democrats. Since it was conservatives who invented the German system of social entitlements, a century ago, conservatives today do not regard them with the same emotions as right-wing Republicans in the United States. Tolerance for unemployment is lower among the Christian Democrats than it is among Republicans here, and there's more reluctance to think of it simply as an economic phenomenon. Because of the deep involvement of the churches in the disarmament movement over the years, German conservatives are less ready than Americans to treat it as the opposition. They are more inclined to regard it as part of their natural constituency, which has to be persuaded and brought along.

Above all, relations with Eastern Europe are not an abstraction to Mr. Kohl's constituents. The ability to move back and forth across that eastern border, for business but especially for purely personal reasons, to visit friends and relatives left behind in the great westward migrations of the post-war years, is a matter of central importance to German voters, and that access rises and falls with the changing climate of East-West relations. Mr. Kohl probably didn't get into all that with Mr. Reagan. But the basic message was that American conservatives cannot afford to become so preoccupied with their adversaries that they lose sight of their friends.