Luggage & Travel Glossary
Plain-language definitions of terms used across our guides and tools.
- Personal item
- The smallest bag allowance most airlines permit free of charge — a purse, small backpack, or laptop bag that fits under the seat in front of you.
- Linear dimensions
- The sum of a bag's length, width, and height (L+W+H). Some airlines — Singapore Airlines among them — size cabin or checked bags by this total rather than by each side separately.
- Spinner wheels
- Four wheels, each able to rotate 360°, letting the bag roll in any direction while upright. The current standard on most carry-on and checked luggage.
- Inline (rollerblade) wheels
- Two fixed wheels at the base of the bag, requiring you to tilt and drag it. Fewer moving parts than spinners, often more durable on rough terrain.
- Polycarbonate
- A durable, somewhat flexible hardside luggage material that resists cracking better than ABS plastic, at a typically higher price.
- Expandable zipper
- A secondary zipper that unzips to add extra depth (usually 2–8 cm) to a suitcase. Expanding a bag can push it over an airline's size limit — measure it expanded if you plan to travel that way.