Subject-verb agreement means that your verb must be conjugated, or changed, to fit (or agree) with the subject. Subjects can be singular or plural. Think of singular and plural as mathematical ...

PRESENT: PAST: PERFECT: ORIGINAL: glide. glided (have) glided. ... the perfect tense is have or had wanted. But, without thinking, we can also conjugate the highly irregular verb to be: I am, I ...