乃 is a literary/classical Chinese word meaning "is" or "therefore." It appears in proverbs and formal writing but is rarely used in everyday spoken Chinese.
The trailing left-falling 丿 stroke is the indexing Kangxi radical for 乃. It groups 乃 with other cursive 丿-radical entries (久, 之, 乏) where the dictionary-lookup anchor is a single sweeping diagonal at the end of a fused glyph.
pictograph
乃nǎi
then; thereupon; thus
Originally a pictograph traditionally read as depicting a woman's breast in profile, later reused for the function-word meaning 'thereupon'. The 2-stroke silhouette is too fused to split into independent named pieces beyond exposing the indexing radical.
