How to understand "It may precede or follow something."? From my perspective, "precede" means something happens earlier than another thing, however, "follow" means that something happens after another thing. Why can they use together to express the same meaning? Chronic bronchitis — Chronic bronchitis is defined as a chronic productive cough for three months in each of two successive years in a patient in whom other causes of chronic cough (eg, bronchiectasis) have been excluded [7]. It may precede or follow development of airflow limitation [7,9]. This definition has been used in many studies, despite the arbitrarily selected symptom duration.Why can they be used together to express the same meaning?