The compound 'two-tenths' is a transparent and modern English formation, directly combining the cardinal number with the fractional unit. The element 'two' descends from the Proto-Indo-European root dwóh₁, a fundamental numeral that gave rise to its equivalents across many Indo-European languages. 'Tenth' originates from the Old English word for 'ten', itself from the PIE root déḱm̥t, combined with a suffix to form ordinals and, by extension, fractional nouns. The logic of the compound is purely mathematical, literally denoting "two of one-tenth parts," which simplifies to the fraction 2/10 or 1/5. Its formation follows the same analytic pattern as other English fractional expressions like 'three-quarters' or 'seven-eighths'.

Structure: two (number) + tenths (fractional unit) - two: From Old English twā, of Germanic origin; related to Dutch twee and German zwei, from an Indo-European root shared by Latin duo and Greek duo. Functions as the cardinal number. - tenths: From Old English tēoþa (tenth), from tīen (ten) + the ordinal suffix -þa. The modern form 'tenths' adds the plural '-s'. It functions as the fractional noun unit.