Filing my 2023 tax return I have come across the term "earned income" while calculating the child care expenses. Where in the Income Tax Act is "earned income" defined?

On the T1 General page 2 you calculate your total income, followed by net income on page 3 and finally taxable income on page 4. No where during the determination of taxable income does "earned income" appear. My taxable income is $35,610 my child care expenses are $15,555 yet I can only deduct $2,393 of those expenses when determining my taxable income. I should be able to deduct or transfer to my spouse the remaining $13,162. not being able to deduct the $13,162 results in having to pay $2,845 in tax.