What are aspect and modality in English grammar?Add examples.

Aspect and mood (modality) are concepts in English grammar
that are tied in with tense and are therefore sometimes difficult to untangle and
understand on their own. Aspect identifies whether the
action, state, or occurrence (event) represented by the verb is complete
or incomplete.

Regarding
aspect, if the verb relates to Sally baking a pie and she
has completed baking the pie, the aspect is
perfect and is expressed as have +
-ed participle as in "Sally has baked the pie." If the verb
refers to Betty baking a pie and she is having trouble and therefore the baking is
incomplete the aspect is
progressive and is expressed as be
+ -ing participle as in "Betty is [still] baking the
pie."

Therefore, what is called Perfect
tense is the Perfect aspect associated with the three tenses, Past,
Present, Future, to yield Past Perfect, Present Perfect, and Future Perfect. What is
called Progressive tense is the Progressive aspect
associated with the three tenses yielding Past, Present, or Future Progressive.
Additionally, what is called Perfect Progressive tense is
the Perfect aspect and Progressive aspect in combination and together associated with
the three tenses to yield Past Perfect Progressive, Present Perfect Progressive, and
Future Perfect Progressive, which is expressed as have + be +
-ing participle as in the Past Perfect Progressive expression,
"Betty had been baking her pie a long
time."

Mood, or modality,
indicates the grammatical tone with which a sentence is
delivered in writing or speech. This is different from personal moods or tones such as
irritation or joyfulness. Grammatical moods are indicative, interrogative,
imperative, conditional, and
subjunctive.

Indicative
is the expression of ordinary statements: Betty is slow with her
pie.
Interrogative is the expression of
questions: Why is Betty slow with her
pie?
Imperative is the expression of the urgent
and commands: Betty, hurry up!
Conditional is the
expression of the probability between related events with modal
verbs and if: If Betty
could finish her pie, it might be good. Also written as:
Betty's pie might be good, if she could finish
it.
Subjunctive is the expression of wishes or
doubts with were and
if: If I were Betty, I would like to
be faster.