dimensionlessly

Etymology tree
Proto-Indo-European *dwóh₁
Proto-Indo-European *d(w)is-
Proto-Italic *dis-
Latin dis-
Proto-Indo-European *meh₁-
Proto-Italic *mētis
Latin mētior
Latin dīmētior
Proto-Indo-European *-tis
Proto-Indo-European *-Hō
Proto-Indo-European *-tiHō
Proto-Italic *-tiō
Latin -tiō
Latin dīmēnsiōder.
English dimension
Proto-Indo-European *lewh₁-
Proto-Indo-European *lewHs-der.
Proto-Germanic *leusaną
Proto-Germanic *lausaz
Proto-Germanic *-lausaz
Proto-West Germanic *-laus
Old English -lēas
Middle English -les
English -less
English dimensionless
Proto-Indo-European *leyg-der.
Proto-Germanic *līkąder.
Proto-Germanic *-līkaz
Proto-Germanic *-ê
Proto-Germanic *-līkê
Proto-West Germanic *-līkē
Old English -līċe
Middle English -ly
English -ly
English dimensionlessly
From dimensionless + -ly.