Summoning condition

Sometimes, conditions exist as prerequirites and/or limitations for "Summoning" a monster to the field.

This card cannot be Special Summoned
This is a blanket Summon Condition, and forbids the card to be Special Summoned by any means, be it from the hand, Deck, Graveyard, or Remove from play pile.

This card cannot be Special Summoned from the Graveyard.
A less harsh restriction than above, this enables cards to be Special Summoned from the hand, Deck, or Removed from Play pile, but not the Graveyard. That said, you could use Monster Reincarnation to move cards with this limitation to your hand from your Graveyard.

This card can only be Special Summoned by...
This places a restriction on how the card must be first Special Summoned. The card cannot be Special Summoned by an external effect until the summoning condition has been properly fulfilled, after which, the monster in question may be summoned like cards such as Monster Reborn. If the card was sent to the Graveyard before being summoned correctly, it cannot be Special Summoned; likewise, if the card was Special Summoned correctly the first time, but is then sent from the field or the Graveyard back to the Deck, the summoning conditions are then reset.

This card cannot be Special Summoned except by...
This is much like the first example, but this time, it allows the card to be Special Summoned by one effect or conditions only, and cannot be Special Summoned by cards such as Monster Reborn. LV Monsters support cards (e.g. Level Modulation) get around this by including the text "ignoring the Summoning conditions" in their card text. However, even with this restriction lifted, such cards can only Special Summon monsters from the Graveyard that have been properly Summoned first. "Level Up!" is able to bypass this completely, since it Special Summons directly from the Deck.

This card cannot be Normal Summoned or Set.
Blanket statement, in no circumstances can the card either be Set face-down, or Normal Summoned/Tribute Summoned. This is included on all "Special Summon-only" cards.

This card cannot be Normal Summoned.
Slightly different to the first condition, a monster can still be Set face-down with this limitation.

This card cannot be Normal Summoned or Set except by...
This is much like the first two examples, but this time, it allows the card to be Normal Summoned or Set by one effect or conditions only, and cannot be Normal Summoned without fulfilling this requirement. This is typically used to prevent the card from being Normal Summoned by Mausoleum of the Emperor.

If you Tribute Summon this card by tributing 3 monsters...
These card grant you an option to Tribute 3 monsters for the Tribute Summon to activate an effect. You can, however, still Tribute Summon this card by offering two Tributes. You cannot use Mausoleum of the Emperor to pay 3000 Life Points to summon these monsters in order to activate their effect(s).

Fusion Summoning Conditions
All Fusion Monsters that do not include contrary summon conditions must be Fusion Summoned properly first, or else they cannot be Special Summoned again from the Graveyard or Removed from Play pile.

This card cannot be Special Summoned except by Fusion Summon.
Blanket statement; used predominantly on Elemental Heroes. This means that, even if you Fusion Summon the card correctly first, you cannot Special Summon it again afterwards. This also means you cannot use cards such as Metamorphosis or Cyber-Stein to directly Special Summon the Fusion Monster(s) from the Fusion Deck.

A Fusion Summon of this card can only be conducted with the above Fusion Material Monsters.
This means that, for a Fusion Summon to take place with this card, you must use the Fusion Material Monsters listed on the card. However, if there are no further summon conditions, you can still Special Summon the monster directly from the Fusion Deck with cards such as Metamorphosis or Cyber-Stein.

This card can only be Ritual Summoned by...
This means that the Ritual Monster must first be Ritual Summoned with the correct Ritual Spell Card, before it can be Special Summoned by another effect.

Summon Monster Effects
Some monsters have their summoning requirements or methods listed as their effect(s), such as with Gate Guardian or Cocoon of Evolution. This 'effect', is neither a Continuous Monster Effect, since it is only 'active' in the hand, nor is it an Ignition Monster Effect, since the 'effect' can be unlocked at theoretically any point in a Duel for most effects, bar a few that require specific monster(s) as Tribute(s), which can only be done in your Main Phase 1 or Main Phase 2.