1) Chemical compound 2) Compound 1) Silicone 
A siloxane is a functional group in organosilicon chemistry with the Si–O–Si linkage. The parent siloxanes include the oligomeric and polymeric hydrides with the formulae H(OSiH2)nOH and (OSiH2)n. Siloxanes also include branched compounds, the defining feature being that each pair of silicon centres is separated by one oxygen atom. The siloxan...
Generally refers to alkylalkoxysiloxanes that are oligimerous (i.e. siloxane or low molecular weight with the polymer consisting of two, three, or four monomers). As with other silicones, application is accompanied by chemical bonding to the substrate if silicate minerals are present. Oligomerous siloxanes are properly classified as penetrants.
[n] - any of a large class of compounds that have alternate silicon and oxygen atoms
noun any of a large class of compounds that have alternate silicon and oxygen atoms