A ruler or tape measure would commonly be used to measure the width of a book.
You measure it.
With a ruler..... hahaha
Height by width and a ruler. :)
Millimetres
the metric system
You would typically use inches to measure a paperback book. You can measure the length, width, and thickness of the book in inches to determine its size.
A centimetre should suffice.
It depends on what is being measured. The instruments and units used for measuring the length, width and height of a building would be different to those used for a matchbox!
instruments are technically used to enhance are sense to discover new things. Such as a telescope and a microscope.
A centimetre, although you could use a millimetre for greater accuracy.
To measure clints and grikes in a limestone pavement, you can use a tape measure, calipers, or a ruler to measure the width and depth of the features. Additionally, a compass can help determine the orientation of the clints and grikes.
Inches or centimetres are fine for a book's dimensions. Measure the width, height and depth to determine the volume. If you are talking about the length of the book's narrative, word count is probably the most accurate.