特に

Of 特(とく) (toku, “special”, noun) plus に (ni, particle).

• IPA^(key): [to̞kɯ̟ᵝ ɲ̟i]

特(とく)に • (toku ni) 

1. specially

   この菓子(かし)はこの催(もよお)しのために特(とく)に調製(ちょうせい)された。

   Kono kashi wa kono moyōshi no tame ni toku ni chōsei sareta.

   This cake has been specially prepared for the occasion.

2. particularly, especially

   特(とく)に欲(ほ)しいものはない。

   Toku ni hoshii mono wa nai.

   There's nothing that I really want.

   • 1938, 中谷宇吉郎 [Nakaya Ukichiro], 雪 [yuki, snow]:

     特(とく)に風(かぜ)のない静(しず)かな夜(よる)のうちに出来(でき)、翌朝旭日(よくあさあさひ)に輝(かがや)いていることが多(おお)い。

     Toku ni kaze no nai shizuka na yoru no uchi ni deki, yokuasa asahi ni kagayaite iru koto ga ōi.

     Particularly when it forms on calm, windless nights, it often sparkles in the morning sun the next day.

The combination of a noun + the particle に (ni) is a standard adverb construction, but it sees much more use in this form than any other.