Horizontal means that something is level or flat. A horizontal line is a line that goes from left to right and does not go up or down. A horizontal plane is a flat surface that does not slope up or down.
Some examples of horizontal things include:
The table was horizontal.
Noun: horizontality.
Adjective: horizontal.
Adverb: horizontally.
The word "horizontal" comes from the Latin word "horizontalis", which means "level" or "parallel to the horizon". It was first used in English in the 16th century.
The word "horizontal" is now used to describe something that is level or parallel to the ground. This can be used to describe something that is literally level, such as a table, or something that is figurative, such as a line of thought.
What items around you are horizontal?