Published April 2026 • Reference

Retirement Terms You Actually Need to Know

The retirement planning world loves jargon. RMDs, HYS, tax-deferred, tax-free, the 4% rule — if you're new to this, it can feel like everyone's speaking a different language designed to make you feel like you need to hire someone to translate it for you.

You don't. Here's a plain-English breakdown of every term that matters, grouped by topic so it actually makes sense.

Account Types

These are tax-deferred retirement accounts. You contribute pre-tax dollars — meaning you get a tax break today — and the money grows without being taxed along the way. The catch: every dollar you pull out in retirement is taxed as ordinary income. The government was patient, but they always get their cut eventually.

A 401(k) is employer-sponsored (your job offers it). A 403(b) is the same thing, just for employees of nonprofits, schools, and hospitals. A Traditional IRA is one you open yourself, independent of your employer.

The account everyone wishes they'd maxed out ten years ago. With a Roth, you contribute after-tax dollars — no tax break today — but the money grows completely tax-free and qualified withdrawals in retirement are tax-free too. You already paid the tax; now you're done with the IRS on that money forever.

The Roth IRA has income limits (high earners eventually can't contribute directly), but the Roth 401(k) through an employer has no income limit. There are workarounds for high earners — that's a whole other post.

If you're early in your career and expect to earn more later, Roth almost always wins. Pay taxes now at your lower rate, withdraw later tax-free at your higher one.

A regular investment account with no tax advantages — no deduction going in, no tax-free growth. You invest after-tax dollars, and you pay taxes on dividends and capital gains as they occur. The upside: no contribution limits, no withdrawal restrictions, no age rules. It's just an investment account.

In retirement planning, it's often the first account you tap because of its flexibility and because the tax treatment of long-term capital gains (0%, 15%, or 20% depending on your income) can actually be quite favorable.

A savings account — typically at an online bank — that pays a significantly higher interest rate than a standard bank savings account. It's still FDIC-insured and still cash, so there's no market risk. The interest you earn is taxed as ordinary income. Think of it as a parking spot for your emergency fund or short-term cash that at least tries to keep pace with inflation.

Contributions & Limits

Free money from your employer. When your company offers a 401(k) match, they agree to contribute to your retirement account based on how much you contribute — typically something like "50 cents for every dollar you put in, up to 6% of your salary." If you're not contributing at least enough to get the full match, you are leaving compensation on the table. Full stop.

Once you turn 50, the IRS lets you contribute extra money to your retirement accounts above the standard annual limit. It's their acknowledgment that a lot of people didn't save enough in their 30s and 40s and need to make up ground.

For 2025, the standard 401(k) limit is $23,500 per year. If you're 50 or older, you can add an extra $7,500 on top of that — $31,000 total. For IRAs, the standard limit is $7,000, with an additional $1,000 catch-up for those 50 and older. If you're in the home stretch before retirement, use this.

Tax Concepts

Tax-deferred means you postpone paying taxes until later — Traditional IRA and 401(k) contributions work this way. You get the deduction now, but you'll owe taxes when you withdraw. The government is essentially giving you an interest-free loan on your tax bill.

Tax-free means the money is never taxed again — Roth accounts work this way. You pay taxes upfront on contributions, but the growth and qualified withdrawals are completely off the IRS's radar in retirement.

Neither is universally better. It comes down to whether you expect your tax rate to be higher now or in retirement — and most people genuinely don't know the answer without running the numbers.

The IRS has been patient about letting your Traditional IRA and 401(k) grow tax-deferred — but they're not going to wait forever. For individuals born before 1960, RMD starts at age 73, born 1960 or later, RMDs kick in at age 75. The IRS requires you to withdraw a minimum amount each year from those accounts, whether you need the money or not. Those withdrawals are taxable income.

The amount is calculated based on your account balance and your life expectancy according to IRS tables. If your Traditional accounts have grown very large, RMDs can push you into a higher tax bracket than you planned for — which is why managing the size of your Traditional accounts before 73 is such an important strategy.

Roth IRAs are not subject to RMDs during your lifetime, which is one of their biggest long-term advantages.

The gradual increase in prices over time — which is just another way of saying your money buys less every year. Historically, the U.S. has averaged around 3% annual inflation, though it swings significantly in both directions. A dollar today will have roughly the purchasing power of about 55 cents in 20 years at that rate.

This is why the calculator uses inflation-adjusted projections. Showing you a future balance of $2 million sounds great until you realize $2 million in 25 years might feel more like $1 million in today's dollars.

Market & Strategy Terms

The S&P 500 is an index of 500 of the largest publicly traded companies in the United States — Apple, Microsoft, Amazon, and 497 others. It's the most common benchmark for "the stock market" in general conversation.

Historically, the S&P 500 has returned roughly 10% per year on average going back to 1928 — though "average" is doing a lot of work in that sentence. Individual years have ranged from catastrophic losses (down 38% in 2008) to spectacular gains (up 32% in 2013). The average is what you get if you stay invested across decades, not what any given year looks like.

After adjusting for inflation, the real historical return is closer to 7% annually. That's the number worth remembering when you're setting assumptions in a calculator.

The single most powerful concept in long-term investing, and the reason starting early matters more than almost anything else. Compound interest means you earn returns not just on your original investment, but on all the returns you've already earned. Your money makes money, and then that money makes money.

$10,000 invested at 7% for 30 years becomes roughly $76,000. Wait 10 years to start and invest the same $10,000 for 20 years — you get about $39,000. Same investment, same return, half the result. That's compounding.

A widely cited guideline for how much you can withdraw from your portfolio each year in retirement without running out of money. The idea: if you withdraw 4% of your portfolio in year one and then adjust that amount for inflation each subsequent year, historical data suggests your portfolio survives a 30-year retirement in most scenarios.

It comes from the "Trinity Study," a 1998 research paper that backtested withdrawal rates against historical market returns. It was designed for a 30-year retirement window, which means it may not be conservative enough for someone retiring at 55 who might need their money to last 40+ years.

The 4% rule is a useful starting point, not gospel. Your actual safe withdrawal rate depends on your specific asset allocation, your flexibility to cut spending in bad markets, and how long you need the money to last. The calculator lets you model your specific situation rather than relying on a one-size-fits-all rule.

The Bottom Line

None of these concepts require a finance degree. They require understanding what you're dealing with so you can make decisions that actually make sense for your situation. The calculator is built around all of these terms — once you understand them, the inputs and outputs will make a lot more sense.

If there's a term you keep running into that isn't here, let me know. This list will grow.