Guidelines for Examination - Table of Contents   PART C GUIDELINES FOR SUBSTANTIVE EXAMINATION   CHAPTER II CONTENT OF A EUROPEAN PATENT APPLICATION (OTHER THAN CLAIMS)   CHAPTER II Annex UNITS RECOGNISED IN INTERNATIONAL PRACTICE AND COMPLYING WITH RULE 49(11) (see II,...       1. SI units and their decimal multiples and submultiples     1.3 Prefixes and their symbols used to designate certain decimal multiples and submultiples

Factor Prefix Symbol Factor Prefix Symbol 10 24 yotta Y 10-1 deci d 10 21 zetta Z 10-2 centi c 10 18 exa E 10-3 milli m 10 15 peta P 10-6 micro µ 10 12 tera T 10-9 nano n 10 9 giga G 10-12 pico p 10 6 mega M 10-15 femto f 10 3 kilo k 10-18 atto a 10 2 hecto h 10-21 zepto z 10 1 deca da 10-24 yocto y

The names and symbols of the decimal multiples and submultiples of the unit of mass are formed by attaching prefixes to the word 'gram' and their symbols to the symbol 'g'.

Where a derived unit is expressed as a fraction, its decimal multiples and submultiples may be designated by attaching a prefix to units in the numerator or the denominator, or in both these parts.

Compound prefixes, that is to say prefixes formed by the juxtaposition of several of the above prefixes, may not be used.