…以上/以下/以內/以外grammar point · tier 2 · scalar bound 以上/以下/以內/以外 (and above / and below / within / beyond a quantity)
Sets a quantity as a boundary marker, then names which direction the open range runs from it: 以上 that figure and up, 以下 that figure and down, 以內 inside the limit, 以外 past it.
字源 FORM what the parts do
The quantity is the mark on the scale. 以 takes that mark as the point to measure from. The direction word opens the range: 上 the territory above it, 下 below it, 內 the side inside the limit, 外 the side past it.
故事 STORY a scene to remember it by
A number is nailed to the ruler. 以 stands on it and points; the arrow runs up, down, inward, or outward, and everything the arrow sweeps is meant.
字源記憶法
框 · Frame
[quantity/age/measure] + 以 + {上|下|內|外}
觸 · Trigger
You have a figure and you mean a span on one side of it, not the figure alone.
序 · The move
1Fix the figure that marks the edge (兩個小時, 十八歲, 一千元, 五公尺).Is it a number, age, price, or measured distance — the kind of thing that sits on a scale?
2Pick the direction word for the range you mean.Bigger/higher → 上; smaller/lower → 下; not exceeding a limit → 內; past the limit → 外.
3Set the figure first, then 以, then the direction word, with no measure word between 以 and 上/下/內/外.Reads as 數量以上/以下/以內/以外, the four chars 以X glued tight.
例 · Examples
1在臺灣，十八歲eighteen years old以下and below (that age)不能cannot買酒buy alcohol。
In Taiwan, anyone under eighteen cannot buy alcohol.
With 以, the noun before is a quantity and 上/下/內/外 names a span on a scale; without 以, the noun is a place and 上/下/內/外 names a physical side (on the table, outside the house).
…多 (over, more than)
兩個小時多 is two hours plus a bit, sitting just past the figure; 兩個小時以上 is two hours and everything above it, an open range upward.
十八歲下 ✗ → 十八歲以下 ✓ (the bound sense needs 以; bare 下 reads as a physical position)
以上五公尺 ✗ → 五公尺以外 ✓ (the figure leads, 以X follows; and the right direction for past-a-distance is 外)
一千元以內的禮物 spent at 一千五 ✗ → keep it 一千元以內 (以內 caps at the figure; spending past it leaves the range)
English puts the word first — over two hours, under eighteen — so learners reach for 上/下 before the number, or drop 以 entirely. Chinese fixes the figure first, then 以, then the direction.