A feature that identifies and highlights misspelled words, and lets you choose among possible correct replacements.

Inline spell-checking is available in Vim since version 7. It can be turned on with the command:

:set spell spelllang=en_us

where en_us is the name of the dictionary to use as reference. While it is running, it will highlight words using four different colors:

SpellBad    word not recognized                 |hl-SpellBad|
SpellCap    word not capitalised                |hl-SpellCap|
SpellRare   rare word                           |hl-SpellRare|
SpellLocal  wrong spelling for selected region  |hl-SpellLocal|

After moving the cursor on a misspelled word, z= can be used to get a list of replacement candidates. If the word is highlighted as misspelled, but you still think it is correct, you can add it to the dictionary instead, using zg.

To turn the feature off, use:

:set nospell

Full documentation: spell vimdoc