[transitive] extend something to make something longer or larger
・ to extend a fence/road
・There are plans to extend the subway line.
…Oxford Learner’s Dictionary “extend”
[intransitive, transitive] to become greater in size, number, or importance; to make something greater in size, number, or importance
Metals expand when they are heated.
Student numbers are expanding rapidly.
A child’s vocabulary expands through reading. The waist expands to fit all sizes.
…Oxford Learner’s Dictionary “expand”