Amino group in aniline is o, p-directing and activating in
electrophilic substitution reactions.

Explanation

In aniline, `NH_(2)` group increases the electron density at o and p-position due to its strong `+R` effect. As such it is an activating and o, p-directing group. However, when aniline is nitrated by nitrating mixture (conc. `HNO_(3)+` conc `H_(2)SO_(4)`) it gives a substantial amount of m-nitroaniline. This can be explained as follows :

In acidic medium used during nitration, the `NH_(2)` group present in aniline gets protonated (due to the protons provided by the acid).
The `-NH_(3)^(+)` group present in anilinium ion is an electron withdrawing group and hence is `m-` directing. As such direct nitration of aniline under controlled conditions gives a large amount of unexpected m-product (nearly 47%).