Accretion describes a lawful increase that attaches automatically to property or to a beneficiary’s entitlement, without a separate transfer.In property law, land gained gradually and imperceptibly by natural forces along watercourses or the foreshore accrues to the riparian or coastal owner. The legal boundary moves with gradual accretion but not with sudden change (avulsion). Across England and Wales, Northern Ireland and Ireland this is a common-law rule; in Scots law the phenomenon is called alluvion, with broadly equivalent effect. Registration may require evidence and an application to amend the title plan or cadastral map.In succession and trusts, accretion denotes the increase of one beneficiary’s share when another gift fails, lapses or is disclaimed, typically among joint tenants or among residuary beneficiaries, unless the instrument shows a contrary intention or statutory anti-lapse applies (for example, Wills Act 1837, s.33; Succession Act 1965 (Ireland), s.98). Specific legacies to tenants in common usually do not accrete; the failed share falls into residue or on intestacy.In Scots conveyancing, accretion also describes after-acquired title “feeding” an earlier disposition by a non-owner, becoming effective when the granter later acquires title; the English and Northern Irish analogue is the doctrine of feeding the estoppel.