A star of spectral type A whose spectrum additionally contains very strong metallic lines (hence the suffix ‘m’) more typical of type F. Am stars are usually members of close binary systems. They rotate more slowly than normal A stars, probably due to tidal interactions with their binary companions, thereby allowing some elements to sink and others to rise in their atmospheres, which produces the observed abundance anomalies. Typical anomalies include enhanced strontium and yttrium and weak calcium and scandium. Sirius is an example of an early Am star.