Answer: True

Reason:

Step 1 - Modern definition

• Oxidation = increase in oxidation number (loss of electrons)
• Reduction = decrease in oxidation number (gain of electrons)

Step 2 - Example

$$\underset{+2}{Cu^{2+}} + 2e^- \longrightarrow \underset{0}{Cu}$$

Copper goes from $+2$ to $0$ — the number decreases, so it is reduced.

Step 3 - Another example

$$\underset{+7}{MnO_4^-} \longrightarrow \underset{+2}{Mn^{2+}}$$

From $+7$ to $+2$ — a decrease of 5 units, so manganese is reduced.

Step 4 - Memory aid

OIL RIG — Oxidation Is Loss, Reduction Is Gain (of electrons).

Also: the oxidation number moving down the number line means reduction.