Consider these two sentences:
- When we go home, we can then watch a DVD
- When we go home, then we can watch a DVD
Both mean the exact same thing, but do they differ in linguistic terms?
No linguistic difference in terms of construction. However, reading the sentences, the first feels more like the going home is a required step of watching the DVD whereas the second just feels like they're events that follow in time. They both result in the same sequence of events, but one indicates for a causal relationship rather than casual.