Say, you've been on friendly terms with someone for years. One Christmas day, you receive a gift from the other person – a Rolex watch, for example (suppose people value this sort of thing) – with a thank you note saying you deserve the gift for all the wonderful things you've done for him or her over the years. It is your first Rolex watch and you find your ruminating how your friendship first began. But you can't remember. Certainly neither of you handed out a Rolex watch to the other on the first day of your acquaintance. A slight nod of the head was more likely it. But as to who started the ball rolling in terms of building a serious relationship, and when, you have no idea. You can't put a firm hand on that. Call it the chicken-or-egg thing – whoever offered the other an olive branch first, one thing led to another and your friendship has grown till this day and that's the most important thing.

Don't know if this is a good example, but I hope you get an idea of the chick-or-egg thing. In standard form, it's "which comes first, the chicken or the egg?" In actual use, this expression may vary into the "chicken-or-egg question", or "chicken-and-egg situation", or "chicken-or-egg paradox".

Here are media examples:

1. Most such deals raise capital in spite of constraints posed by credit ratings or financial covenants. But it's impossible to separate structured finance from the accounting methods corporations use to achieve it. That raises the chicken-or-egg question underscored by recent scandals: Can the deal stand on its economic merits or does it depend on favorable accounting?

"The fundamental rationale for structured financing is the value it creates" by unlocking otherwise inaccessible capital, argues Andrew T. Feldstein, head of structured financing products at JPMorgan Chase. "The vast majority of structured finance transactions were done for good economic reasons. The anecdotes you hear about are the ones that were done badly."

- See-Through Finance, CFO Magazine, October 1, 2002.

2. The basic unit of life is the cell (i.e. the prokaryote). What is a cell? A modern cell is a lipid-protein membrane enclosing a volume of chemicals at different concentrations. A cell is very complex. It has a selectively permeable membrane to allow certain molecules in or out. A cell has various metabolic pathways that help maintain cell integrity, and therefore prolong the existence of its complexity. A simple lipid bilayer is impermeable to polar molecules. On the other hand, a protein membrane is quite "leaky", allowing all kinds of molecules to pass through. A cell must retain certain molecules while removing others. For example, if a cell just had a simple lipid membrane enclosing different chemicals, simple chemical reactions would go to "completion" or to equilibrium. More chemicals would need to be brought in and waste products would need to be removed.

It's the classic "the chicken or the egg" paradox. Which came first, the membrane or the cytoplasm? Did a membrane develop first to allow various chemicals in and out? Or were the chemicals concentrated enough to allow metabolism before the membrane developed? Similarly, how did the genetic system develop? Did the proteins come first or the genetic code?

- Origins of Life: The Chicken or the Egg? Geocities.com.

3. The relationship between diabetes and depression apparently cuts both ways: Not only are people with treated type 2 diabetes at a heightened risk for developing depression, but individuals with depression are also at risk for developing diabetes. It's a classic chick or egg question, because doctors don't know which one comes first – the diabetes or the depression.

- Diabetics are more depressed, new studies show, Bet.com, June 18th, 2008.