Name change is the legal act by a person of adopting a new name different from their current name.
The procedures and ease of a name change vary between jurisdictions. In general, common law jurisdictions have loose procedures for a name change while civil law jurisdictions are more restrictive.
A pseudonym is a name used in addition to the original or true name. This does not require legal sanction. Pseudonyms are generally adopted to conceal a person's identity, but may also be used for personal, social or ideological reasons.
Marriage or civil partnership (e.g. Tiffany Rodriguez marries Aanchal Chaudhari and assumes her surname, becoming Tiffany Chaudhari)
Adoption, or marriage of a custodial parent
Divorce or estrangement of parents
Immigration / adaptation of the name to a different language or script (e.g. Samantha Ogden became Shilpa Ojha on becoming an Indian national)
General dislike of one’s name
To evade the law or a debt or commit fraud
To avoid a stalker or harassment
Religious conversion and/or deconversion, ordination or return to lay status (e.g., Cassius Clay to Muhammad Ali upon conversion to Islam)
To choose a surname associated with a hobby, interest, or accomplishment (e.g., old name Henry Schifberg, new name Henry Lizardlover)
To receive an inheritance conditional on adopting the name of the deceased (this reason was once quite common in landowning families in the UK)
To replace a name which might be considered undesirable with a more desirable one (e.g., old surname Lipschitz, new surname London)
To dissociate themselves from a famous or infamous person (e.g., old name Michael Jackson, new name Martin Jackson)
To identify with a famous or infamous person (e.g., old name Simon Johnson, new name Simon Pendragon)
To dissociate themselves from a family black sheep (e.g., relatives of Adolf Hitler).
To dissociate themselves from an ethnic origin (e.g., changing Battenberg to Mountbatten or Jan Ludvik Hoch to Robert Maxwell).
Commercial sponsorship, e.g., Jimmy White temporarily became Jimmy Brown for HP brown sauce.