A synthesis reaction, also known as a composition reaction, is characterized by the reaction of two or more substances chemically joining to form a single product.
Here are three examples
Magnesium metal reacts with oxygen to produce magnesium oxide
##2 Mg + O_2 -> 2MgO##
In this next example, sodium reacts with chloride to form table salt.
##2Na + Cl_2 -> 2 NaCl##
In the examples above, two different react to form a compound.
In the last example, two different react to form a new compound which is a single product.
Calcium oxide reacts with sulfur dioxide to produce calcium sulfite.
##CaO + SO_2 -> CaSO_3##
