Your total income minus specific adjustments. This is the starting point for calculating your tax liability. Includes wages, interest, dividends, business income, and retirement distributions, less certain deductions like student loan interest and self-employed retirement contributions.
Your AGI with certain deductions added back. Used to determine eligibility for various tax benefits like Roth IRA contributions and premium tax credits. The exact calculation varies depending on the tax benefit in question.
The original cost of an asset for tax purposes, adjusted for things like improvements, depreciation, or reinvested dividends. Critical for calculating capital gains or losses when you sell the asset.
The profit or loss from selling an asset. Short-term applies to assets held one year or less (taxed as ordinary income); long-term applies to assets held more than one year (preferential tax rates apply).