截然不同
jié rán bù tóng · HSK 7
entirely different
⚫⚪ 截然 = cut + so → cleanly cut apart; 不同 = not same: split like black and white
截 means to cut/sever and 然 marks a manner, so 截然 reads as cut-cleanly or sharply; tack on 不同 (not same) and you get two things severed apart with no overlap, as opposite as black and white.
截 — semantic 戈 (halberd) + phonetic 雀 (sparrow, simplified to 隹 above 土)
截 originally depicts cutting with a dagger-axe (戈), giving the core meaning 'to cut off' or 'sever.' The 戈 component carries the meaning while the rest of the character supplies the sound. Over time it broadened to include senses like 'intercept,' 'block,' or 'a section/length' of something.
不 — single pictograph; bird flying upward
Originally a pictograph in oracle bone script, traditionally interpreted as a bird flying up toward the sky and unable to come down, suggesting negation or refusal. Over time it became the standard negation word in Chinese, used before verbs and adjectives to mean 'not'.
同 — 冂 enclosure + 一 + 口 mouth
Originally depicted multiple mouths gathered under one cover or enclosure, suggesting people speaking together in agreement. From this image of voices joining, it came to mean 'same,' 'together,' or 'alike.' The shared cover symbolizes unity.