Amendment of pleading

What does Amendment of pleading mean in American Law?

The definition of Amendment of pleading in the law of the United States, as defined by the lexicographer Arthur Leff in his legal dictionary is:

All procedural systems provide means pursuant to which a pleading may be amended; the resulting changed pleading is called thereafter an “amended pleading.” Frequently, especially early in a proceeding, a pleading may be amended without leave of court or consent of the other party; it is often called an “amendment as of course.” Thereafter, pleadings may be amended, but only with such leave or consent, in order better to state a claim or defense; under modem practice leave is freely

given if the amendment will not unduly prejudice the other party. Indeed an “amendment to conform to the evidence” (or “proof”) may also be permitted during or even after trial if there is a divergence between what was alleged and the evidence [at] trial, but again only if the other party would not be unduly prejudiced. See also departure. Under some circumstances a judge may compel amendment or amend a pleading on its own motion, e.g., to excise scandalous or prejudicial material. See Fed. R. Civ. P. 15 for the current Federal procedural rule on amendment of pleading.