ben
Synonym discussion
Sense: preposition/1
Ben, inside, within, and in can all point to an interior place, but ben is the unusual one. Ben is a Scots word and sounds local or old-fashioned in most modern English, while inside is the normal everyday choice. Within is more formal and is common in writing, rules, and measured limits, as in 'within the walls' or 'within two days'. In is the broadest and least marked word, but it is less precise because it can describe many relationships, not only interior space. Also remember that the mountain-name ben has a different history from the Scots word meaning 'inside'. Compare: 'Come ben' sounds Scots, 'come inside' is neutral, and 'stay within the fence' is more formal.
Etymology
This entry brings together two different historical words that ended up with the same spelling. The adverb and preposition ben continue an Old English inside-word, 'binnan', which survived in Scots with the meaning 'within'. The noun sense has a separate source: it comes from Scottish Gaelic 'beinn', meaning a mountain peak, and remains visible in names such as Ben Nevis and Ben Lomond. So when learners meet ben in place names, they are seeing a Gaelic naming element, not the same word as the Scots ben meaning 'inside'.