Float (Slack)
The amount of time an activity can slip without delaying the project or a successor.
Float, or slack, measures schedule flexibility: how long an activity can be delayed without causing a downstream impact. Total float equals Late Start minus Early Start (or Late Finish minus Early Finish) and is the leeway before the project end date slips. Free float is narrower: how long an activity can slip before delaying any immediate successor. On the exam, free float is always less than or equal to total float for a given activity, and critical-path activities carry zero total float by definition. Watch near-critical paths, since small float erodes quickly.
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