Every LaTeX writer has one. You might not have chosen it consciously, but somewhere along your first hundred equations, your fingers picked a default — and now it’s less a technical decision than a personality trait.
Quick comparison: equation vs align vs gather
| Environment | Best for | Numbering | Alignment |
|---|---|---|---|
equation | A single displayed equation | One number | Centered by default |
align | Multi-line derivations or equations aligned at an equals sign | One number per row; use align* for none | Aligned at & |
gather | Several equations displayed together without shared alignment | One number per row; use gather* for none | Each row centered independently |
\[ ... \] | A displayed formula that needs no number | None | Centered by default |
eqnarray | Legacy documents; prefer align for new work | One number per row | Three columns; spacing around relations can be excessive |
Load \usepackage{amsmath} to use align, gather, and their starred forms. In numbered rows, use \notag to suppress an individual number.
That’s the practical difference. Now for what your default says about you.
equation
The institutional choice. Numbered, respectable, exactly one equation at a time. People who default to equation cite theorems by number, keep their references in order, and probably have a .bib file that doesn’t embarrass them. The paperwork of mathematics, filled out correctly.
align
The workhorse. Once you’ve derived anything across multiple lines — an & here, a \\ there — you never quite go back. align people are process people: they want you to see how they got there, step by step, aligned at the equals sign like a well-organized argument.
The dark side: align users have all, at some point, used it for a single equation out of pure muscle memory.
gather
The rarest breed. Multiple equations, centered, no alignment — gather says “these belong together, but I refuse to impose a relationship on them.” Honestly, I respect it. Choosing gather means you know align exists and decided your equations deserve to stand on their own.
\[ ... \]
The minimalist. No number, no name, no ceremony — just math, displayed, gone. \[ people write quickly and don’t look back. They’ll tell you most equations don’t need numbers, and they’re right, and it’s still slightly unsettling how little they care.
(If you write $$ ... $$ instead: I see you. TeX purists would like a word, but I see you.)
eqnarray
Ah. So you learned LaTeX from a thesis template last touched in 2003, passed down through your lab like an heirloom nobody examines too closely.
Here’s the thing nobody in that lab told you: eqnarray has been considered obsolete for decades. The spacing around the equals sign is subtly, famously wrong — wide enough that amsmath’s documentation politely pretends it doesn’t exist. Every eqnarray in the wild is a small archaeological record of how LaTeX knowledge actually spreads: not through documentation, but through inherited templates and the phrase “just copy what the last student did.”
Switch to align. It takes five minutes. Your equals signs will thank you.
(If you knew all this and use eqnarray anyway: you are a chaos agent, and I’d love to know what else is in your preamble.)
For the record
I’m a gather person. I like my equations centered, independent, and free of imposed relationships — which, now that I write it down, may explain more about me than about my typesetting.
What’s yours?
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