Rome wasn't built in a day.

Expression: "Rome wasn't built in a day."

Meaning: The Roman Empire, which spanned parts of Europe, Africa, and Asia, literally wasn't built in a day. In fact, it took a very, very long time. Although current projects are not likely to take nearly as long, the expression has evolved to mean that something will at least not be completed quickly.

Example: "This new project is going to take time. Rome wasn't built in a day."

All Bark and No Bite

Expression: "all bark and no bite"

Meaning: This idiom originated with dogs, the type that bark loudly and may seem scary, but they don't actually attack. Over time this expression has evolved to refer to people, who obviously don't bark like dogs, but they talk tough and make threats that they don't actually follow through on.

Example: "He threatened to punch me in my face, but he's all bark and no bite."

Go the Extra Mile

Expression: "go the extra mile"

Meaning: First of all, one must understand that Americans measure long distances in miles, not kilometers. Once you understand that, think of this idiom in terms of running and other distance-related activities. Going an extra mile means putting forth extra effort to go a longer distance. Over time this expression has evolved to mean putting forth extra effort whether or not distance is an issue.

Example: "I had a lot of stuff to move this weekend, and my friends really went the extra mile to help me out."

Hard Nut to Crack

Expression: "hard nut to crack"

Meaning: Some nuts, such as peanuts, crack open relatively easily. Cracking open some other nuts, however, can require more physical effort. So while some problems can be easy to solve, like the ease with which you can crack open peanuts, this idiom developed as a way to refer to other problems, like hard-to-crack nuts, that are more difficult to solve.

Example: "This crossword puzzle is a hard nut to crack."

Out of My League

Expression: "out of my league"

Meaning: Think of this in terms of sports leagues. Because of having less athletic ability, a lower league team cannot be expected to compete and win versus an upper league team. Over time, this has evolved to mostly describe romantic relationships. Someone who is "out of your league" is perhaps very attractive, or very wealthy, or famous, or in some way is someone who cannot be expected to develop a romantic interest in someone so much less attractive, less wealthy, not famous, and so forth.

Example: "I am in love with my favorite movie actress, but she's out of my league."

Fork in the Road

Expression: "fork in the road"

Meaning: A fork in a road is when one road, like the handle of a fork eating utensil, branches off in multiple directions and the driver suddenly has to choose which branch to continue on. Even when not driving, however, this phrase has evolved to mean that one has reached the time to make a decision about something.

Example: "My cellphone died, and so I have come to a fork in the road; should I buy a new Samsung smartphone or a new iPhone?"

... and a cherry on top.

Expression: "... and a cherry on top"

Meaning: When making a sundae you add ice cream, maybe some fruit, maybe some candies, and then probably some whipped cream. The cherry on top represents not only completion, but also that everything wanted is included. The cherry itself is just a little bit extra. Over time, the phrase has evolved to mean not only that everything is included, even when ice cream is not involved, but a little bit extra as well.

Example: "My new car has GPS, satellite radio, heated seats, and a cherry on top."