(N/A) Combination reaction: $A$ combination reaction may be denoted as $A + B \rightarrow C$. Either $A$ or $B$ or both must be in the elemental form for such a reaction to be a redox reaction.
$C_{(s)} + O_{2(g)} \xrightarrow{\Delta} CO_{2(g)}$
$3 Mg_{(s)} + N_{2(g)} \xrightarrow{\Delta} Mg_{3}N_{2(s)}$
$CH_{4(g)} + 2 O_{2(g)} \xrightarrow{\Delta} CO_{2(g)} + 2 H_{2}O_{(l)}$
$(b)$ Decomposition reaction: These are the opposite of combination reactions. $A$ decomposition reaction leads to the breakdown of a compound into two or more components,at least one of which must be in the elemental state.
$2 H_{2}O_{(l)} \xrightarrow{\Delta} 2 H_{2(g)} + O_{2(g)}$
$2 NaH_{(s)} \xrightarrow{\Delta} 2 Na_{(s)} + H_{2(g)}$
$2 KClO_{3(s)} \xrightarrow{\Delta} 2 KCl_{(s)} + 3 O_{2(g)}$
Note: All decomposition reactions are not redox. Example: $CaCO_{3(s)} \xrightarrow{\Delta} CaO_{(s)} + CO_{2(g)}$
$(c)$ Displacement reaction: An ion or atom in a compound is replaced by an ion or atom of another element,denoted as $X + YZ \rightarrow XZ + Y$. These are categorized into metal and non-metal displacement.
$(i)$ Metal displacement: $A$ metal in a compound is displaced by another metal in the uncombined state. Examples:
$CuSO_{4(aq)} + Zn_{(s)} \rightarrow Cu_{(s)} + ZnSO_{4(aq)}$
$V_{2}O_{5(s)} + 5 Ca_{(s)} \rightarrow 2 V_{(s)} + 5 CaO_{(s)}$
$TiCl_{4(l)} + 2 Mg_{(s)} \rightarrow Ti_{(s)} + 2 MgCl_{2(s)}$
$(ii)$ Non-metal displacement: Includes hydrogen displacement and rare oxygen displacement reactions.