The same character can have multiple titles in game and can be difficult to remember. So the FEH commmunity uses abbreviated names to refer to them.
Examples:

• B!Lucina : the prefix "B" means "Brave" (check below the list of prefixes)
• Corrin(M) : the suffix "M" means "Male" (check below the list of suffixes)

Prefixes

Here is the list of prefixes used on this website (generally the lower case letters are omitted by the community)

By theme

• NY!

  New Year (banners at the beginning of the year)
• HSp!

  Hostile Spring (january 2019)
• De!

  Desert (banners in january from 2021 to 2025) (names on game8 : Plegian, Hatari, Sage, Nabata, Jehanna)
• I!

  Ilia (january 2026)
• V!

  Valentine (can also be called "DoD", Day of Devotion) (banners in february)
• Sp!

  Spring (banners in march)
• Y!

  Young (banners in april)
• Pic!

  Picnic (april 2019)
• Gr!

  Groom (males in wedding banners) (banners in mai)
• Br!

  Bride (females in wedding banners) (banners in mai)
• Su!

  Summer (banners in july & august)
• HSu!

  Hoshidan Summer (august 2018 & 2024)
• P!

  Pirate (august 2020 & 2021)
• Th!

  Thieves (august 2022)
• T!

  Tea (august 2023 & 2025)
• Da!

  Dance (september 2017, 2019 & 2020 ; only composed of refreshers) (names on game8 : Performing, Soiree, Masquerade)
• S12!

  Scions of Twelve (september 2021)
• FT!

  Fire Tribe (september 2022)
• WT!

  Wind Tribe (september 2023)
• IT!

  Ice Tribe (september 2024)
• Fe!

  Ferox (also called Arena or Gladiator) (september 2025)
• H!

  Halloween (banners in october)
• N!

  Ninja (banners in november)
• W!

  Winter (banners in december)

By trait

• Ai!

  Aided
• As!

  Ascended
• At!

  Attuned
• E!

  Emblem
• Et!

  Entwined
• R!

  Rearmed
• F!

  Fallen
• C!

  Chosen
• L!

  Legendary
• M!

  Mythic
• D!

  Duo
• H!

  Harmonized

Other

• 35!

  35th anniversary (only used for 35!Marth, a new duo Marth released for the 35th anniversary of the Fire Emblem franchise)
• B!

  Brave (heroes chosen by the community in the CYL events)
• Ad!

  Adrift (name of Paralogue 27)

Suffixes

Here is the list of suffixes used on this website.

• (M)

  Male
• (F)

  Female
• (A)

  Adult
• (Y)

  Young
• (SoV)

  Shadow of Valentia (refers to the Fire Emblem game released in 2017)
• (FE{N})

  Refers to the {N}-th Fire Emblem game

The list of Fire Emblem games be found here.

The suffix can also be used as prefix by the community (ex: F!F!Corrin ; meaning Fallen Female Corrin)