grammar → 簡直
TSUMUGU · TBCL 4 (est.) · 語法
簡直 grammar point · tier 1 · 簡直 downright / simply (it amounts to the extreme)
· jiǎnzhí
Marks an exaggerated verdict: drop every qualification and treat the claim as effectively reaching its extreme — it as good as IS so.

字源 FORM what the parts do

簡 caps bamboo (竹) over 間 for the sound, jiān risen to jiǎn; one slip holds little, so the sense slips to brief. 直 runs a straight line up from an eye (目), looking dead ahead with no turn. Brief and straight together: cut the qualifying short and go plainly to the end.

故事 STORY a scene to remember it by

A pointer skips every mark on the scale and lands hard against the far end.
字源自撰記憶法
框 · Frame
[subj] 簡直 (是) [extreme assessment]
觸 · Trigger
Your assessment is so strong you want to drop the hedging and call it the extreme outright.
序 · The move
1Put 簡直 right before the assessment, after the subject.Is it adverbial on a whole judgement, not stuck before a plain noun on its own?
2Pitch the assessment at its extreme — 不可能, 太…了, 一樣, a strong adjective or a vivid comparison.Is the claim pushed to the limit? A measured statement does not want 簡直.
3Add 是 before a noun-phrase verdict (簡直是…); leave it out before an adjective or verb.Does what follows need the copula?
例 · Examples
1一天in one day寫好finish writing一篇論文a paper簡直downright, simply不可能的事an impossible thing
Finishing a whole paper in one day is downright impossible.
界 · Boundary
幾乎
幾乎 stops just short of the mark (almost, nearly); 簡直 jumps to the mark and treats it as reached (it as good as IS).
根本
根本 goes to the root and states the basic truth, often a flat denial (not at all, fundamentally); 簡直 inflates an assessment to its limit for force.
真的
真的 affirms a claim is literally true; 簡直 is exaggeration — the claim is treated AS IF it hit the extreme, not measured as fact.
他簡直天才。 ✗ → 他簡直是天才。 ✓ (a noun verdict takes 簡直是)
這個問題簡直難。 ✗ → 這個問題簡直太難了。 ✓ (the assessment must be pitched to the extreme, not a bare adjective)
他簡直比你高一點。 ✗ → 他簡直跟你一樣高。 ✓ (簡直 pushes to the limit, not a small measured difference)
English "simply/literally" is used loosely for emphasis on any claim; learners attach 簡直 to mild statements where the exaggeration to an extreme is missing.