noun which may take the genitive case particle 'no', noun
highest ever; record-high; most on record
Used in news and formal contexts to describe a number or amount that is the highest since records began. Often modifies a following noun with の.
This summer's temperatures hit a record high.
There were a record number of applications.
史上最高 also means 'highest in history', but is more general and can refer to quality or achievement, while 過去最多 specifically refers to a countable number or amount.
過去最大 means 'largest ever' and is used for scale or size, whereas 過去最多 is for countable numbers.
Compound of 過去 (past) and 最多 (most numerous). A straightforward modern coinage used in statistics and reporting.