Definition of "closest"

In sober seriousness, there is more poetry than truth in the sweet poem of Allan Cunningham—the Town and Country Child: witness the cheerful voices of the rosy faces to be met with in the smallest street and closest alley in London;...

1831, L[etitia] E[lizabeth] L[andon], chapter V, in Romance and Reality. […], volume II, London: Henry Colburn and Richard Bentley, […], page 93

The closest affinities of the Jubulaceae are with the Lejeuneaceae. The two families share in common: (a) elaters usually 1-spiral, trumpet-shaped and fixed to the capsule valves, distally […]

1992, Rudolf M[athias] Schuster, The Hepaticae and Anthocerotae of North America: East of the Hundredth Meridian, volume V, New York, N.Y.: Columbia University Press, page 4