Risk-based performance

"The possibility that a given event will occur. Terms sometimes take on more specific connotations, with “likelihood” indicating the possibility that a given event will occur in qualitative terms such as high, medium, and low, or other judgmental scales, and
“probability” indicating a quantitative measure such as a percentage, frequency of occurrence, or other numerical metric."

Source : COSO Integrated Risk Management Framework

Chance of something happening.

Note: The word "likelihood" is used to refer to the chance of something happening, whether defined, measured or determined objectively or subjectively, and described using general terms (such as unlikely, likely, almost certain) or mathematically (such a probability or a frequency over a given time period).

Source : BS31100:2008 [ISO Guide 73, modified]