This is the 50th most frequent Tamil word.
அத
"அத" means "that" in English.
Here, 'அத' ('that') is a demonstrative pronoun referring to a distant object.
அத எனது நண்பனின் புத்தகம்.
That is my friend's book.
Here, 'அதை' ('that') serves as the object of the verb 'saw' in the sentence.
அதை நான் பார்த்தேன்.
I saw that.
Here, 'அது' ('that') functions as the subject of the sentence, indicating the topic being discussed.