In the context of C++ vectors, the terms "size" and "capacity" refer to different aspects of the vector.

Size: The size of a vector represents the number of elements currently stored in the vector. It indicates the actual number of elements that have been inserted into the vector.

• For example, if a vector has 5 elements, its size is 5. You can obtain the size of a vector using the size() member function of the vector, like this: myVector.size().

Capacity: The capacity of a vector represents the maximum number of elements that the vector can hold without requiring reallocation of memory. It represents the allocated storage space in the vector, which is usually greater than or equal to the size of the vector.

• When you initially create a vector or add elements to it, it dynamically allocates memory to accommodate the elements. The capacity specifies the maximum number of elements that can be stored in the vector without triggering a reallocation.
• You can obtain the capacity of a vector using the capacity() member function of the vector, like this: myVector.capacity().
• It's important to note that the capacity may be larger than the size, and the capacity can change dynamically as elements are added or removed from the vector. When the vector's capacity is reached and more elements need to be added, the vector automatically reallocates memory to increase its capacity.

In summary, the size of a vector refers to the number of elements currently stored in the vector, while the capacity represents the maximum number of elements that the vector can hold without requiring reallocation.