In the early days of printing presses and typeface blocks, letters that would otherwise look strange or take up too much space when placed side-by-side were carved together on the same block. Called ligatures, these interacting letter combinations optimized the rest of the line's spacing and improved the overall readability of the word or the sentence. Adobe InDesign automatically inserts ligatures -- provided the font is designed to support them -- although this setting can be disabled when the feature is unnecessary or unwanted.
Expose the Character panel if it isn't already open by clicking the "Window" menu and selecting "Type" followed by "Character."
Use your cursor to highlight the text from which you'd like to remove the ligatures.
Expose the Character panel's "Options" menu. It is a small downward-facing arrow and four horizontal lines located at the top of the panel.
Click "Ligatures" -- which, if enabled, has a check mark beside it -- to disable the feature.
Use your cursor to highlight the text containing the ligatures.
Click on the "Options" menu icon, which is located at the far right of the Control Panel and looks like a small downward-facing arrow and four horizontal lines.
Click "Ligatures" to uncheck and disable the option.
InDesign substitutes standard lowercase ligatures like "fi" and "fl" in OpenType, PostScript or TrueType fonts.
With OpenType fonts, InDesign also supports the use of discretionary ligatures, which are more ornate, optional combinations -- like those used in "Th" and "st." Enable or disable discretionary ligatures by opening the "Options" menu on the Control Panel and selecting the "OpenType" option.
Information in this article applies to Adobe InDesign CS6 or CC. It may vary slightly or significantly with other versions or products.