In a large pitcher, stir together lemon juice and sugar until completely dissolved.
Stir in water until combined.
Serve chilled, poured over ice.
If you want to get fancy, dip the rims of the chilled glasses in lime juice, then in sugar. Pour in chilled limeade. Garnish with a lime slice and add a fancy straw.
Notes
Add more lime juice or more sugar to suit your tastes.