so-called
Word family
Synonym discussion
Sense: adjective/1
All four words question the accuracy of a label, but they differ in tone and context. 'Alleged' carries a legal or accusatory weight — it suggests someone may have done something wrong without proof (e.g. 'the alleged thief'). 'Ostensible' is formal and points to the surface-level reason that may hide a real one (e.g. 'the ostensible purpose of the meeting'). 'Purported' is similar to 'alleged' but slightly more neutral — it just signals that something is claimed to be true (e.g. 'the purported benefits of the diet'). 'Self-styled' applies only to people who give themselves a title without official recognition (e.g. 'a self-styled expert'). 'So-called' is the most versatile and common of the group — you can use it for things, people, ideas, or labels without suggesting legal wrongdoing. For everyday disagreement with a description, 'so-called' is usually the best choice: 'The so-called bargain turned out to cost twice as much.'
Etymology
The compound 'so-called' grew out of the phrase 'so called,' meaning 'called or named in that way.' It first appeared as a single hyphenated word in the 1600s, originally in a neutral sense (simply 'known as'). By the 1800s, writers had started using it to express doubt about a label's accuracy, giving rise to the modern disapproving sense. The explanatory sense (introducing a new term) developed alongside the neutral use.