Anything done, or said; an act or action; an actual occurrence; a circumstance; whatever comes to pass; an event. (Dictionary of Law, W.C. Anderson, Chicago, 1889.)
By Lord Nicholls of Birkenhead in Re H (minors),  AC 563 at para 94:
94. Thus far I have concentrated on explaining that a court’s conclusion that the threshold conditions are satisfied must have a factual base, and that an alleged but unproved fact, serious or trivial, is not a fact for this purpose. Nor is judicial suspicion, because that is no more than a judicial state of uncertainty about whether or not an event happened.
95. I must now put this into perspective by noting, and emphasising, the width of the range of facts which may be relevant when the court is considering the threshold conditions. The range of facts which may properly be taken into account is infinite. Facts include the history of members of the family, the state of relationships within a family, proposed changes within the membership of a family, parental attitudes, and omissions which might not reasonably have been expected, just as much as actual physical assaults. They include threats, and abnormal behaviour by a child, and unsatisfactory parental responses to complaints or allegations. And facts, which are minor or even trivial if considered in isolation, when taken together may suffice to satisfy the court of the likelihood of future harm. The court will attach to all the relevant facts the appropriate weight when coming to an overall conclusion on the crucial issue.