Salaams... Brother you said, "in languages there are words of expressions" these usually are cultural and so differ from culture to culture. For example when we sneeze we say, "Alhumdulillah" where as in the English Western world people ask to be "Blessed" or "Excused." In Islam there aren't fixed expressions though we do often have praises of Subhanallah, Alhumdullillah, Astaghfirullah and the like. Furthermore we refer to each other as brother and sister and that should generate love and mercy between us as the verses below elaborate.
Surah Al Hujurat Verses 11-13:
11. O you who believe! Let not a group scoff at another group, it may be that the latter are better than the former; nor let (some) women scoff at other women, it may be that the latter are better than the former, nor defame one another, nor insult one another by nicknames. How bad is it, to insult one's brother after having Faith [i.e. to call your Muslim brother (a faithful believer) as: "O sinner", or "O wicked", etc.]. And whosoever does not repent, then such are indeed Zalimun (wrong-doers, etc.).
12. O you who believe! Avoid much suspicions, indeed some suspicions are sins. And spy not, neither backbite one another. Would one of you like to eat the flesh of his dead brother? You would hate it (so hate backbiting) . And fear Allah. Verily, Allah is the One Who accepts repentance, Most Merciful.
13. O mankind! We have created you from a male and a female, and made you into nations and tribes, that you may know one another. Verily, the most honourable of you with Allah is that (believer) who has At-Taqwa [i.e. one of the Muttaqun (pious - see V.2:2)]. Verily, Allah is All-Knowing, All-Aware.
Your brother in Islam