₂ Subscript Two
Subscript two (₂) is the character used in chemical formulas — H₂O, CO₂ — and for the second index in a sequence.
Also known as: subscript 2, subscript two, h2o subscript, co2 subscript, small 2 below.
Codes
| Symbol | ₂ | |
| Full run 0-9 | ₀₁₂₃₄₅₆₇₈₉ | |
| Unicode | U+2082 | |
| HTML entity (decimal) | ₂ | |
| HTML entity (hex) | ₂ | |
| CSS | \2082 | |
| LaTeX | x_2 | |
| Windows Alt code | Alt + 8322 |
How to type ₂ (Subscript Two)
Alt + 8322 works in apps that accept decimal-Unicode Alt input (Word among them). There is no short Alt + 0nnn code. Elsewhere press Win + . (period) and search “subscript”, or copy ₂ above.
No default keystroke. Open Character Viewer (Control + Cmd + Space) and search “subscript two”, or copy ₂ above.
Type 2082, then press Alt + X to get the character ₂. Note Word's AutoCorrect already turns H2O into H₂O-style *formatting* automatically in some locales — that is formatting, not this character.
Insert → Special characters, then search “subscript two”.
In math mode write H_2O. For real chemistry use the mhchem package: \ce{H2O} typesets the formula correctly, including the subscripts.
Usage
- ₂ is the chemistry subscript: H₂O, CO₂, O₂, N₂. Because it is a character and not formatting, the formula stays intact when pasted into a spreadsheet cell, a filename, a code comment or a chat message.
- In math and stats, x₂ is the second element of a sequence and σ₂ the second standard deviation.
- For a document you control end to end, the word processor's subscript button gives better typography — it scales with the font. Use ₂ when the text has to leave the document intact.
- Do not confuse it with ² (U+00B2 SUPERSCRIPT TWO), which sits above the line and means squared. x² and x₂ are entirely different claims.