Endlessness, unlimitedness, absence of a beginning, end or limits to size.
"The concept of infinity suggests an endless expanse where there is no beginning, no end, and no limit to its size."
In plain English: Infinity means something that goes on forever without ever ending.
"The number line extends to infinity in both directions without ever ending."
Usage: Use infinity to describe something without any limit in quantity, extent, or duration, such as an endless supply or the vastness of space. Avoid confusing this abstract concept with specific large numbers; instead, emphasize that it represents a state beyond all measurable bounds rather than just being very big.
The word "infinity" comes from the Latin term infinitas, which means "unlimitedness." It was formed by combining the negative prefix in- ("not") with fīnis ("end").