forty-ninth parallel 
The parallel of latitude 49° north of the equator, especially as forming the boundary between Canada and the US west of the Lake of the Woods.
- turn (or put) back the clock
- turn (or tighten) the screw (or screws)
- turn out
- turnout
- turn over
- turnover
- turn over a new leaf
- turnpike
- turnpike road
- turnround
- turn round and do (or say) something
- turn signal
- turnsole
- exodermis
- exodus
- exoenzyme
- ex officio
- exogamous
- exogamy
- exogenic
- exogenous
- exogenously
- exoglossic
- exon
- exonerate