[possessive] hairline
hairline 常与物主代词连用，表示某人的发际线。
His hairline is receding.
他的发际线在后退。
发际线
细线；发丝线；细微裂缝；细裂纹；发丝钓线；额头上头发开始生长的线；书写、绘画或排版中的极细线。
The line along the forehead where the hair begins to grow.
额头上头发开始生长的线
The line along one's forehead where hair starts growing.
书写、绘画或排版中的极细线。
A very thin line in writing, drawing, or typography.
极细的裂缝。
A very thin fissure.
由头发制成的钓鱼线
A fishing line made from hair.
He has a receding hairline.
他的发际线在后退。
用法提示：此处hairline指额头头发生长的边缘线。
She styled her hair to hide her high hairline.
她打理发型以掩盖高高的发际线。
用法提示：此处hairline指发际线的位置。
The barber carefully trimmed along his hairline.
理发师沿着他的发际线仔细修剪。
用法提示：此处hairline指引发际线的线条。
hairline 常与物主代词连用，表示某人的发际线。
His hairline is receding.
他的发际线在后退。
hairline 作定语时表示细小的，如 hairline crack（细裂缝）。
There's a hairline crack in the vase.
花瓶上有一道细缝。
常与 at 搭配表示位置。
The scar is at the hairline.
疤痕在发际线处。
grammar · medium
易错句子He has a high hair line.
正确表达He has a high hairline.
发际线是一个复合名词，应写成一个单词，而非分开的两个词。
grammar · medium
易错句子My hairline are receding.
正确表达My hairline is receding.
hairline是可数名词单数，谓语动词应用单数形式“is”，而非复数“are”。
对“细缝”或“细线”义项的反义，指较粗的线条或缝隙。
hairline指发际线或细缝，headline指新闻标题或头条
发际线后移；变高的发际线
He used a new treatment to deal with his receding hairline.
他使用一种新疗法来应对自己的发际线后移。
骨裂；细微裂纹
The X-ray revealed a hairline fracture in her wrist.
X光片显示她的手腕有一处骨裂。
细微裂缝
A hairline crack runs along the edge of the mirror.
镜子边缘有一道细微裂缝。
极微小的差距
The candidate won the election by a hairline margin.
那位候选人以极其微小的票数差距赢得了选举。
hair
hair + cut
hair + do
hair + pin
hair + brush
out + line
hair（头发）+ line（线），复合词，无前缀/后缀；同根词：haircut（理发）、hairbrush（发刷）、underline（下划线）、outline（轮廓）
发际线就是沿前额上方头发开始生长的那条线。
头发从头皮长出，发际线是头皮上有发区域与无发区域的分界。
发际线在头部两侧靠近太阳穴的位置形成清晰的边线。
刘海覆在前额，通常沿着发际线修剪。
常与 hairline 搭配，指发际线逐渐向上移动的现象。
Dictionary facts from ECDICT, WIKTIONARY.