← ← leftwards arrow, U+2190 ISOnum
↑ ↑ upwards arrow, U+2191 ISOnum $4
→ → rightwards arrow, U+2192 ISOnum
↓ ↓ downwards arrow, U+2193 ISOnum
↔ ↔ left right arrow, U+2194 ISOamsa
↵ ↵ downwards arrow with corner leftwards = carriage return, U+21B5 NEW
⇐ ⇐ leftwards double arrow, U+21D0 ISOtech (ISO 10646 does not say that lArr is the same as the 'is implied by' arrow but also does not have any other character for that function. So lArr can be used for 'is implied by' as ISOtech suggests)
⇑ ⇑ upwards double arrow, U+21D1 ISOamsa
⇒ ⇒ rightwards double arrow, U+21D2 ISOtech (ISO 10646 does not say this is the 'implies' character but does not have another character with this function so rArr can be used for 'implies' as ISOtech suggests)
⇓ ⇓ downwards double arrow, U+21D3 ISOamsa
⇔ ⇔ left right double arrow, U+21D4 ISOamsa