The difference between Casual and Informal

When used as adjectives, casual means happening by chance, whereas informal means not formal or ceremonious.

Casual is also noun with the meaning: a worker who is only working for a company occasionally, not as its permanent employee.

check bellow for the other definitions of Casual and Informal

Casual as an adjective:

Happening by chance.

Examples:

"They only had casual meetings."
Casual as an adjective:

Coming without regularity; occasional or incidental.

Examples:

"The purchase of donuts was just a casual expense."
Casual as an adjective:

Employed irregularly.

Examples:

"He was just a casual worker."
Casual as an adjective:

Careless.
Casual as an adjective:

Happening or coming to pass without design.
Casual as an adjective:

Informal, relaxed.
Casual as an adjective:

Designed for informal or everyday use.

Casual as a noun (British, Australian, NZ):

A worker who is only working for a company occasionally, not as its permanent employee.
Casual as a noun:

A soldier temporarily at a place of duty, usually en route to another place of duty.
Casual as a noun (UK):

A member of a group of football hooligans who wear expensive designer clothing to avoid police attention; see .
Casual as a noun:

One who receives relief for a night in a parish to which he does not belong; a vagrant.
Casual as a noun (video games, informal, derogatory):

A player of casual games.

Examples:

"usex The devs dumbed the game down so the casuals could enjoy it."
Casual as a noun (British):

(dated) A tramp.

Informal as an adjective:

Not formal or ceremonious.

Examples:

"an informal get-together"
Informal as an adjective:

Not in accord with the usual regulations.

Examples:

"an informal agreement"
Informal as an adjective:

Suited for everyday use.

Examples:

"'informal clothes"
Informal as an adjective (of language):

Reflecting everyday, non-ceremonious usage.
Informal as an adjective (gardening):

Not organized; not structured or planned.