Formal:
* അന്നൻ (annan) - This is the most formal and respectful way to refer to an older brother.
* ചേട്ടൻ (chettan) - This is also a formal way to refer to an older brother, but it's slightly less formal than "annan".
Informal:
* അണ്ണൻ (annan) - This is a more informal way to refer to an older brother, often used by younger siblings.
* ചേട്ടാ (chettá) - This is an informal way to address an older brother, like "brother" in English.
* ആട്ടേൻ (atten) - This is a very informal and endearing term used by younger siblings.
Other options:
* വയസ്സുള്ള സഹോദരൻ (vayassulla sahadarān) - This literally translates to "older brother" and is a more neutral way to refer to an older sibling.
* സഹോദരൻ (sahadarān) - This simply means "brother" and can be used to refer to an older brother, although it doesn't explicitly specify age.
The best way to choose the right term depends on the context and your relationship with the person you are talking to.