This is the 2549th most frequent Arabic word.
ا
The Arabic letter "ا" (alif) is the first letter of the Arabic alphabet and represents a vowel sound, often a long "a" (as in "father") or used as a placeholder for a glottal stop (hamza).
The word 'أ' is used here as part of the verb 'أحب', meaning 'I love', indicating the first-person singular present tense.
أحب القراءة.
I love reading.
The word 'أ' initiates the interrogative word 'أين', meaning 'Where', used for asking questions.
أين ذهبت؟
Where did you go?
While the word 'ا' may seem absent in this context, it forms part of the definite article 'ال' in 'المطر', meaning 'the rain', used here for definiteness.