Θ Theta Symbol (Uppercase)
Uppercase theta (Θ) is the Greek capital letter — best known to programmers as big-Θ, the tight bound in algorithm analysis.
Also known as: capital theta, uppercase theta, big theta notation, greek capital letter theta.
Codes
| Symbol | Θ | |
| Lowercase | θ · U+03B8 | |
| Unicode | U+0398 | |
| HTML entity (named) | Θ | |
| HTML entity (decimal) | Θ | |
| HTML entity (hex) | Θ | |
| CSS | \0398 | |
| LaTeX | \Theta | |
| Windows Alt code | Alt + 233 |
How to type Θ (Theta Symbol (Uppercase))
Hold Alt and type 233 on the numeric keypad, then release Alt. Note there is no leading zero — Alt + 0233 gives é. (Alt + 920 also works where decimal-Unicode input is supported.)
No default keystroke. Open Character Viewer (Control + Cmd + Space), search “greek capital letter theta”, and double-click Θ.
Type 0398, then press Alt + X to convert it to Θ.
Insert → Special characters, then search “greek capital letter theta”.
Use \Theta in math mode for the upright capital, \varTheta (amsmath) for the italic variant, and \theta for the lowercase θ.
Usage
- In computer science, Θ(n log n) is the tight bound: an algorithm that is both O(n log n) and Ω(n log n). Big-O is an upper bound only, so Θ is the stronger and more precise claim.
- In meteorology and thermodynamics Θ is potential temperature; in solid-state physics Θ_D is the Debye temperature; in mechanics it often denotes an angular displacement whose rate is θ̇.
- Uppercase Θ is the letter; the lowercase θ is the one used for angles and for an unknown parameter in statistics.
- Which one to use: Θ (U+0398) is the Greek capital letter and the character you want. ϴ (U+03F4) is the “theta symbol” variant with the bar reaching the sides, kept in Unicode for compatibility with technical notation. Ø (U+00D8) is a slashed Latin O — a Danish/Norwegian letter, not a Greek one — and ⊖ (U+2296) is circled minus. Only Θ is the letter theta.