Space Characters
NameEntityWidthAlias
Non-Breaking Space [ ]no-break space, NBSP
Narrow No-Break Space [ ]NNBSP
En Space [ ]
Em Space [ ]
3-Per-Em Space [ ]1/3 em space
4-Per-Em Space [ ]1/4 em space
6-Per-Em Space [ ]1/6 em space
Figure Space [ ]numeric space
Punctuation Space [ ]
Medium Mathematical Space [ ]medium space, MMSP
Thick Space  [  ]medium mathematical space, hair space
Thin Space [ ]
Hair Space [ ]very thin space
Whitespace [ ]space, SP
Ideographic Space [ ]
Tag Space󠀠[󠀠]
Zero Width Space​[​]negative space, ZWSP
Zero Width No-Break Space[]BOM, ZWNBSP
Zero Width Joiner‍[‍]
Zero Width Non-Joiner‌[‌]
Word Joiner⁠[⁠]no break
Invisible Times⁢[⁢]
Invisible Separator⁣[⁣]invisible comma
Length Units
NameAbbr.DefinitionSize
elementemFont-Relativefont-size of element/root[]
rem[]
line heightlhline-height of element/root[]
rlh[]
characterchwidth of `0` character in element's/root's font[]
rch[]
X-heightexheight of letter x in element's/root's font[]
rex[]
capital lettercapcapital letter-height of element's/root's font[]
rcap[]
international charactericaverage full-glyph width (based on CJK character `水` (U+6C34)) in element's/root's font[]
ric[]
Smallsv*Viewport-Relativeviewport size keywords[]
Largelv*[]
Dynamicdv*[]
DefaultN/A[]
viewport widthvw1% of viewport's width/height[]
viewport heightvh[]
viewport inlinevi1% of viewport's size in root's inline-axis/block-axis[]
viewport blockvb[]
viewport minimumvmin1% of viewport's width or height, whichever is smaller/larger[]
viewport maximumvmax[]
container query widthcqwContainer Query1% of the queried container's width/height[]
container query heightcqh[]
container query inlinecqi1% of the queried container's inline/block (width/height in horizontal writing-mode) size[]
container query blockcqb[]
container query minimumcqminthe smaller/larger value of either the queried container's inline or block size[]
container query maximumcqmax[]
centimetercmAbsolute1cm  =  37.8px  =  ²⁵.²⁄₆₄in[]
millimetermm1mm  =  ⅒cm[]
quarter-millimeterQ1Q  =  ¹⁄₄₀cm[]
inchin1in  =  2.54cm  =  96px[]
picapc1pc  =  ⅙in[]
pointpt1pt  =  ¹⁄₇₂in[]
pixelpx1px  =  ¹⁄₉₆in[]