Which types of linkages are formed between different monomers to form polymers? Explain the various types of linkages with examples.

(N/A) $\rightarrow$ In a polypeptide or a protein, amino acids are linked by a peptide bond, which is formed when the carboxyl $(-COOH)$ group of one amino acid reacts with the amino $(-NH_2)$ group of the next amino acid with the elimination of a water molecule (dehydration).
$\rightarrow$ In a polysaccharide, the individual monosaccharides are linked by a glycosidic bond. This bond is also formed by dehydration between two carbon atoms of two adjacent monosaccharides.
$\rightarrow$ In a nucleic acid, a phosphate moiety links the $3'$-carbon of one sugar of one nucleotide to the $5'$-carbon of the sugar of the succeeding nucleotide. The bond between the phosphate and hydroxyl group of the sugar is an ester bond. As there is one such ester bond on either side, it is called a phosphodiester bond.
$\rightarrow$ Nucleic acids exhibit a wide variety of secondary structures, such as the Watson-Crick model of $DNA$, where two polynucleotide strands are anti-parallel and held together by hydrogen bonds between nitrogenous bases ($A=T$ with two hydrogen bonds, $G \equiv C$ with three hydrogen bonds).