The two terms weak and strong dollars are used regularly in the forex market. By using these terms ones define the strength and the value of U.S dollar in comparison with other currencies.
When one say the dollar is strong, it means that the U.S dollar has increased its price level as compare to other major currencies that are also on the rise. For instance, the prevailing interest rate between America and Canada stuck among 0.6 CAD/USD to 1.1 CAD/USD. In case exchange rate increases from 0.6 to 0.7 CAD/USD, it would mean that at this point CAD has stronger value as contrast to USD. On the other hand, U.S dollar will only be considered as strong if exchange rates move to 1.1 CAD/USD.
Strengthening and weakening can be applied for any currency but in my example, I was specifically talking about the U.S dollar. A U.S will be considered as strengthening when its value will be increased as contrast to a different currency. This simply means that now U.S will purchase other currencies more in value as compare to the previous occasions. On the other hand, the weakening of U.S dollar means that its value has been decreased as compare to another currency. As a result, US will purchase less of the other currency.