1. What kinds of travel mean "maybe no return": a trip, a voyage, or a journey?
2. Which one always leads you out of town: a road or a street?
3. What's the difference between the beginning of a vacation and its start?
4. Why isn't the Grand Canyon called the Grand Ravine or the Grand Gorge?
5. Are boats always smaller than ships?
1. A journey and a voyage. A trip almost always implies a return. Voyages and journeys are also longer in duration and distance.
2. A road. Both are public ways for vehicles but were originally intended to be distinct. A street is in a village or city and is lined with shops, houses, or buildings. If it isn't, it's supposed to be a road. Often when a town expands, a road becomes a street. Roads usually run between towns, sometimes bearing the name of where they lead.
3. The beginning is the opening moments, as in a program or the first few days of a month. The start is the sudden first action, like the start of a race.
4. A ravine is long and narrow. It is also smaller than a canyon and worn by fast water. A gorge is narrow, steep, and has a stream at the bottom. It may be part of a canyon. A canyon is deep with steep sides and a stream at the bottom.
5. In general, yes. A ship is the larger seagoing vessel, usually over 500 tons. However, a submarine is considered both a boat (U-boat) and a "warship." Boats can be propelled by oars, paddles, sail, or power. Ships are propelled exclusively by sail or power.
SOURCES: 'Room's Dictionary of Distinguishables,' by Adrian Room; Concise Oxford Dictionary; 'Cassell Guide to Related Words,' by Eugene Ehrlick and S.I. Hayakawa; and Webster's Dictionary.