A synthesis reaction or combination reaction is an elementary process in which two or more chemical substances react to generate a single product. Simple elements or compounds that come together to form a more complex compound. The following is the general form presented by this type of compounds:

Where A and B represent any chemical substance and C the resulting compound.

Some synthetic reactions are given by combining a basic oxide with water, to form a hydroxide, or by combining the oxide of a non-metal with water to produce an oxy-acid.

Examples:

Other synthetic reactions are given by combining a non-metal with hydrogen, to obtain a hydrazide.

Example:

Oxidation of a metal is also a synthesis or combination reaction.

Example: Notes

wiki