The small ribonucleoprotein component of RIBOSOMES. It contains the MESSENGER RNA binding site and two TRANSFER RNA binding sites - one for the incoming AMINO ACYL TRNA (A site) and the other (P site) for the peptidyl tRNA carrying the elongating peptide chain.

Synonyms: Subunits, Small Ribosomal, Ribosomal Subunits, Small, Small Ribosomal Subunit, Small Ribosome Subunits, Small Ribosomal Subunits, Subunit, Small Ribosome, Subunits, Small Ribosome, Ribosome Subunits, Small, Small Ribosome Subunit, Ribosomal Subunit, Small, Ribosome Subunit, Small, Subunit, Small Ribosomal