Sam-, sometimes written as san- or sam- is another prefix commonly seen in Pali and Sanskrit Buddhist terms. It is a possible of cognate of the English word same; as well as at least two prefixes. 

One of the prefixes is the Latin prefix com- / con- / co- in the sense of ‘same,’  ‘with,’ or ‘together.’    This should not be confused with con- . contra in the sense of anti or against.   Note that the Spanish word con or com means ‘with.’ the same as the French word avec.  This prefix is seen in the word cosign, to sign with. Also compound; com= together + pound = to put (from the Lain verb ponere).  Also, compassion; com = with the same + passion = suffering or emotion (passion originally meant suffering).

The other one is the Greek derived syn- / sym- / syl-; which has virtually the same meaning; together with, united,  merging, at the same time. An example is sympathy; sym = same = pathy = emotion.  Or synthesis;  syn = together = theses = to put (from the Greek verb meaning to put).

The Chinese for this is 共 {gong / gu}.

There are many common Buddhist terms with this prefix.  Some examples, off the top of my head;  are sanskrit, samsara, sankhara / samskara, samkhata / samskrta, sambodhi, samma / samyak  or samyag, sanna / samjna, and samadhi.

By the way, there is a related prefix sama. This might be sam = same + a =  to or toward {an infix?}.  As such, it has virtually the same meaning as sam-,  with the sense of together.  However, it can also mean even,  level, smooth,  pacified, or calm. It appears that is sometimes written as shama. An example  of this is found in the word samatha / shamatha.