= Glycoside
In its classical oxygen-linked sense, a <glycoside> is a mixed <acetal> derived from a cyclic <monosaccharide>, with the anomeric hydroxy group replaced by an $\mathrm{OR}$ group. The substituent attaches at the <anomeric carbon> through a <glycosidic bond>. The partner recovered after removing the sugar residue is commonly called the <aglycone>.<Nomenclature of Carbohydrates (Recommendations 1996) by Alan D. McNaught>[Section2-Carb-33.1: definitions, classical example and aglycone terminology]{ref}
<Methyl α-D-glucopyranoside> is the nomenclature document's simple example. Comparing it with cyclic <glucose>, replace the anomeric $\mathrm{OH}$ by $\mathrm{OCH_3}$. As an original atom-counting check, the net addition is $\mathrm{CH_2}$, giving $\mathrm{C_7H_{14}O_6}$ from the free glucose formula $\mathrm{C_6H_{12}O_6}$. This is structural bookkeeping, not a proposed one-step laboratory procedure.
Both the ring form and the <anomer> belong to the identity: specifying α-D-glucopyranoside conveys more information than merely saying that a molecule contains <glucose>. The acetal at that centre also differs from the free <hemiacetal> of the parent sugar.
The attachment atom matters to naming. IUPAC discusses oxygen-, sulfur-, nitrogen- and carbon-linked derivatives separately and discourages some broad biochemical uses of the word glycoside. A structural description should therefore state the actual connection rather than treating every sugar-containing molecule as the same class.<Nomenclature of Carbohydrates (Recommendations 1996) by Alan D. McNaught>[Sections2-Carb-33.1 and33.3–33.7: scope and distinct attachment conventions]{ref}
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