Origin: Greek prefix auto-
Automatic has 7 different meanings across 2 categories:
light machine gun
"The soldier fired his automatic at the advancing enemy before reloading."
a pistol that will keep firing until the ammunition is gone or the trigger is released
"The detective realized he was dealing with an automatic weapon when the shots continued without him pulling the trigger again."
A car with automatic transmission.
"I prefer driving a car with automatic because I don't have to shift gears while climbing the steep hill."
In plain English: An automatic is a vehicle that shifts gears by itself without the driver needing to use a clutch pedal.
"The automatic stopped at the red light."
Usage: Use "automatic" as a noun to refer specifically to a vehicle equipped with an automatic transmission rather than manual gear shifting. Do not use this form to describe a person or situation that happens without effort, which requires the adjective form instead.
operating with minimal human intervention; independent of external control
"automatic transmission"
"a budget deficit that caused automatic spending cuts"
resembling the unthinking functioning of a machine
"an automatic `thank you'"
"machinelike efficiency"
Capable of operating without external control or intervention.
"The washing machine's spin cycle is automatic, so it dries and folds the clothes all by itself once the water drains away."
In plain English: Automatic means something that works on its own without you having to do anything.
"The automatic doors opened as soon as I walked inside."
Usage: Use "automatic" to describe something that functions on its own without needing manual input, such as an automatic door or transmission. Do not use it to mean "certain" or "inevitable," which are incorrect applications of the word.
The word automatic comes from the New Latin term automaticus, which combines a root meaning "self-moving" with a suffix that turns it into an adjective. This original sense of moving or acting by itself entered English to describe machines that operate without human intervention.