1
on the [window/door] sill
window sill 指窗台，door sill 指门槛；sill 常与 on 搭配表示位置。
He left his keys on the window sill.
他把钥匙留在了窗台上。
底梁；底槛
先理解核心含义，再看它在真实句子里的用法。
底梁；底槛
a horizontal timber or beam forming the lowest member of a framework or supporting structure
He left his keys on the window sill.
他把钥匙留在了窗台上。
A breast wall; window breast; horizontal brink which forms the base of a window.
马车的辕杆
The shaft or thill of a carriage.
构成框架或支撑结构最底部的连续水平木构件
structural member consisting of a continuous horizontal timber forming the lowest member of a framework or supporting structure
A threshold; horizontal structural member of a building near ground level on a foundation or pilings, or lying on the ground, and bearing the upright portion of a frame; a sill plate.
He wiped dust from the sill before opening the window.
他打开窗户前擦掉了窗台上的灰尘。
A small bird landed on the sill and looked into the room.
一只小鸟落在窗台上，朝屋里张望。
She painted the sill of the kitchen window white last weekend.
她上周末把厨房窗户的窗台漆成了白色。
window sill 指窗台，door sill 指门槛；sill 常与 on 搭配表示位置。
He left his keys on the window sill.
他把钥匙留在了窗台上。
这个结构比 the window sill 稍正式，两者意思相同。
Dust had gathered on the sill of the bedroom window.
灰尘积在卧室窗户的窗台上。
Not this
The cat is sitting in the window sill.
Use this
The cat is sitting on the window sill.
窗台是一个水平的平面，表示物体位于其表面时应用介词 on，而不是 in。in 表示在某个空间或容器的内部，窗台并不是一个封闭的空间，所以用 in 不自然。
Not this
He made a sill mistake.
Use this
He made a silly mistake.
sill 是名词，意为“窗台”或“门槛”；silly 是形容词，意为“愚蠢的”。在修饰名词 mistake 时需要用形容词，因此应把 sill 改为 silly。
Focus on the distinctions below. Other candidates are kept compact until a reliable usage note is available.
窗台
The cat sat on the window sill.
猫坐在窗台上。
门底槛；门槛
He tripped on the door sill.
他被门槛绊了一下。
窗台高度
The sill height is about 90 centimeters.
窗台高度约为90厘米。
底梁；墙底槛
The house's sill plate is bolted to the foundation.
房子的底梁用螺栓固定在地基上。
Use sill naturally, then get feedback on meaning, tone, grammar, and phrasing.
Revisit a common error or keep this word in your review list.
sill 指窗台或门槛，是框架最底部那根横木——想象窗框底下垫着一条石板，像基石托住整扇窗。
语域：neutral 常见场景：建筑、门窗安装 该词多用于建筑和家装语境，指门窗底部或框架底部的水平横木/横梁；在日常口语中常以 window sill、door sill 的形式出现。正式程度偏中性。
这些词都与 sill /sɪl/ 押韵，重读元音和末尾辅音均为 /ɪl/。注意：silly /ˈsɪli/ 和 silk /sɪlk/ 拼写相近，但发音并不与 sill 押韵。
Dictionary facts from ECDICT, WIKTIONARY.